This article explores and compares the political leadership of two successive British Prime Ministers (PMs), Theresa May (2016–2019) and Boris Johnson (2019–2022), in their domestic handling of Brexit. After the EU referendum of June 2016 Brexit presented Westminster with “the greatest challenge of modern times” (McConnell and Tormey 2020, p. 685) and became the primary political issue confronting May and Johnson. In this paper we analyse how each exercised political leadership in the domestic politics of the withdrawal and future relationship negotiations.

Prime ministers have played a central role in “instigat[ing] and espous[ing] government policy towards European integration” (Daddow 2015, p. 72). As the UK’s first post-referendum PMs, Theresa May and Boris Johnson were tasked with extricating the UK from the EU. Although both faced a similar dilemma at the start of their premierships—securing Brexit with a divided party and a small or no parliamentary majority—the outcome was different. May is remembered as another PM who was destroyed by the Europe issue. She repeatedly failed to achieve her central mission—to get parliamentary support for the main element of her Brexit policy, the Withdrawal Agreement. In contrast, Johnson was “the first Conservative leader to triumph over the Europe question, an issue that had undermined Margaret Thatcher, John Major, David Cameron and Theresa May” (Cutts et al. 2020, p. 20). Having partly renegotiated the Withdrawal Agreement inherited from May (Menon and Wager 2021), he navigated this through the House of Commons with a majority of 99, allowing the UK to leave the EU after 47 years of membership on 31 January 2020 (Ford et al. 2021, p. 573). It is in this contrast that our research puzzle lies.

We show in this article that May and Johnson did not face identical political circumstances in which they handled Brexit. Johnson was also able to use different political strategies because some of those used by his predecessor had been seen to fail. However, we argue the explanation does not only arise from a different political context and circumstances. By applying Richard Heffernan’s power resources model, we demonstrate that it also owes much to a different use of power resources that they had available. Unlike May, Johnson made skilful use of the power resources at his command. He possessed more personal power resources and could draw on the available institutional power resources more effectively than May. As a result, he was able to be predominant in his government’s decision-making.

The paper proceeds as follows. The first part provides a literature review and addresses the original contribution of the article. The second section discusses Heffernan’s power resources model underpinning his prime ministerial predominance thesis, the theoretical background of the study. The subsequent empirical analysis investigates similarities and differences between May and Johnson in their political leadership in handling the domestic politics of Brexit by considering (1) their personal power resources and (2) their institutional power resources. Finally, the conclusion points to the limitations of Heffernan’s model and suggests how it can be revised.

Literature review and original contribution

The article’s original contribution is two-fold. First, its chief empirical contribution is to give a fuller account of prime ministerial leadership of the domestic politics of Brexit. It extends the wider literatures on prime ministerial leadership (Allen 2019; Bujard 2019; Worthy and Bennister 2020) and the domestic politics of Brexit (Biermann and Jagdhuber 2021; Heide and Worthy 2019; Figueira 2022; Waylen 2021; Ward and Ward 2021) by systematically analysing their political leadership during the extraordinary circumstances of the post-referendum period, exploring the sources and limits of May’s and Johnson’s leadership.

Much academic work has been done on the leadership of Theresa May in general. Worthy and Bennister (2020) analyse May’s leadership capital index during her first 2 years in office and conclude that she went from being an exceptional leader to a medium capital leader. Byrne et al. (2021) identify May as a disjunctive PM, showing how the conditions and circumstances under which she governed compromised the effectiveness of her actions. Allen (2018) studies May’s political inheritance and leadership after the 2016 referendum, analysing the factors that led to her leadership election victory. Atkins and Gaffney (2020) examine her prime ministerial performance between the 2016 referendum and the 2017 general election through the performance of narratives. Other scholars have devoted attention to aspects of her Brexit policy, especially to the issue of the withdrawal negotiations. Heide and Worthy (2019) focus on May’s use of secrecy around the UK–EU negotiations between 2016 and 2019 to protect her power, policy, and reputation. In other research on the Brexit negotiations, Biermann and Jagdhuber (2021) argue that May was forced to play parallel and overlapping nested games during which she was pressured by both the EU and Brexiteers. In a similar vein, Schnapper (2020) also draws on nested games theory in her account of Brexit negotiations and suggests that May was caught between her hard rhetoric at home and the reality of her bargaining position in Brussels. By contrast, Figueira (2022) combines the two-level game framework with a negotiation psychology lens, exploring the behavioural and psychological incentives behind the UK’s hard negotiation behaviour. Dunlop et al. (2020) look at the UK government’s (mis)management of the Brexit process from June 2016 to May 2019 from a policy learning perspective, whereas Figueira and Martill (2021) draw on insights from bounded rationality to show how the UK’s decision-making environment on Brexit was linked with biased thinking.

Given his recent premiership, there is comparatively little research on Boris Johnson’s leadership, let alone in connection with his approach to Brexit. Waylen (2021) examines the Johnson government’s early Covid response and highlights the prime minister’s hypermasculine leadership style. Ward and Ward (2021) investigate the strategy of executive centralisation in the early stages of the Johnson government in the context of COVID-19 and Brexit. An early assessment of the complete term of Johnson’s premiership has been done from an historical perspective by Seldon and Newell (2023). Despite parallels between the two PMs, there have been no direct attempts to tackle their political leadership and approach to Brexit in a single, comparative analysis. This inquiry attempts to close this research gap, by building upon, extending, and updating the above-mentioned research and providing a first set of comparative insights into May’s and Johnson’s leadership. In doing so, it adds empirical richness to earlier accounts and highlights the value of looking at the domestic politics of Brexit through the lens of political leadership.

Second, our article also makes a theoretical contribution. We apply Heffernan’s model to new areas of inquiry—to new PMs and a new policy area of the domestic politics of the EU withdrawal process. In doing so, we are building on a previous study by Bujard (2019) of British prime ministerial political leadership in European policy before the Brexit referendum, which analysed the 1976–2007 period. Using the empirical cases of May and Johnson, we argue that this comparative perspective is particularly useful here, as it enables us to test and develop the model. The article demonstrates the value of Heffernan’s model whilst also pointing to its limitations and suggesting how it can be revised.

Political leadership and the domestic politics of Brexit: a framework for analysis

We base our analytical framework on the work of Heffernan (2003, 2005, 2010). Heffernan presents an account of prime ministerial predominance which draws upon the work of Rod Rhodes, Patrick Dunleavy and Martin J. Smith on the core executive and combines this with elements of Michael Foley’s presidentialisation thesis (Dunleavy and Rhodes 1990; Foley 1993, 2000; Rhodes 1995; Smith 1994, 1999).

For Heffernan prime ministerial predominance “provides the prime minister with more authority and power than other actors. It enables him or her to be a ‘stronger or main element’ within the core executive, providing them with considerable, but never overwhelming intra-executive influence. […] Predominance enables the prime minister to lead, but not command, the executive, to direct, not control, its policy development, and to manage, but not wholly dominate, the legislature” (Heffernan 2003, pp. 349–350). For Heffernan a predominant prime minister has become an ideal type given that today’s politics “has created a template for the powerful, authoritative political figure, the predominant party leader, who heads up the electoral professional, office seeking political party” (Heffernan 2010, p. 2). We are convinced that this ideal type is no less diminished thirteen years later.

However, predominance does not automatically accompany the office. It depends on several factors: “Predominance grants the prime minister the ‘potential’ for leadership within government, but only when personal power resources are married with institutional power resources, and when the prime minister is able to use both wisely and well” (Heffernan 2003, p. 350). Personal resources include “reputation, skill and ability; association with actual or anticipated political success; public popularity; and high standing in his or her party” (Heffernan 2003, p. 351). In addition, Heffernan identifies four key institutional resources. First, the prime minister can set the government’s policy agenda through control of the cabinet system and influence in Whitehall. Second, she or he can set up a Prime Minister’s Department in all but name using No. 10 Downing Street and the Cabinet Office. Third, they can set the political agenda through effective media management. Lastly, the premier is legally the head of the government. This grants certain rights to lead the government such as “appointing and dismissing ministers, allocating and reallocating ministerial portfolios, overseeing government business, managing the cabinet system, and generally supervising the machinery of government” (Heffernan 2003, p. 357). These resources, when possessed, can result in the premier having much authority and impact within the core executive and make it possible for him or her to be predominant (Heffernan 2003).

As we attempt to find out how much each prime minister could shape the domestic politics of Brexit and whether they were even able to dominate it at times, we find Heffernan’s model particularly useful. This is for four reasons. Firstly, it allows for a targeted investigation of prime ministerial political leadership in a specific policy field or on a specific issue, which is crucial when studying something as intricate and unique as Brexit. Secondly, its specific focus on the power dynamics within the executive and the party make it apt for studying the actions and decisions of May and Johnson who had to navigate complex dynamics within their party, cabinets, and the broader government machinery in managing Brexit. Thirdly, the model’s dual emphasis on the relational (interactions among political actors) and locational (central or peripheral position in the executive) aspects of power in the core executive provides a suitably detailed picture of how power was wielded and contested within the May and Johnson administrations. Fourthly, Heffernan’s recognition of the transient nature of the power resources is particularly relevant given the fluid political landscape during the Brexit process, with shifting allegiances, party divisions, election outcomes and changing public sentiment which affected the leadership of both May and Johnson.

The above reasons underscore why we find Heffernan’s model better suited to help us answer our questions than alternative models such as, for instance, the leadership capital index approach by Bennister et al. (2017). This framework is geared to assessing the overall political leadership of a PM. While its quantitative nature is useful for comparative purposes, it might not fully capture the complexities, nuances, and qualitative aspects of political leadership in a specific policy field or on a specific issue. Also, its focus on capital may not adequately represent the various other aspects of leadership that are important in a PM’s role—for instance, the ability to dominate within the government and the party, a key focus of Heffernan’s model, might be underemphasised. Similarly, while Buller and James’ (2012) statecraft model and Greenstein’s (2009) leadership style model also offer insightful approaches, their heavy emphasis on the strategic skills of leaders and individual leadership styles and qualities respectively might downplay the structural and institutional constraints that shape a PM’s leadership, which are crucial for understanding the challenges faced by May and Johnson during Brexit. Instead, in our view the power resources model finds a good balance in addressing structural and agency factors impacting on a PM’s political leadership.

Importantly, our ambition is not to establish direct causal roles of each resource. Rather, we aim to describe and understand what sources of power the PMs accumulated and how they employed them to address the challenges of implementing Brexit.


We examine May’s and Johnson’s prime ministerial performance between June 2016 (the period right after the EU referendum) and December 2020 (conclusion of the EU-UK Trade and Cooperation Agreement), thus covering the whole withdrawal period. We do not extend our analysis beyond 1 January 2021, the first day of the full implementation of Brexit following the end of the transition phase. From this point onward, the transformed nature of the UK’s relationship with the EU renders the comparison between the two prime ministers less meaningful.

As we argue in detail below, the 2017 and 2019 elections were highly consequential for May and Johnson’s political leadership. We therefore analyse each prime minister’s premiership before and after each election separately. The periods used in the analysis are thus: Theresa May I: July 2016–June 2017; Theresa May II: June 2017–July 2019; Boris Johnson I: July 2019–December 2019; Boris Johnson II: December 2019–December 2020. In what follows, we systematically explore the extent to which May and Johnson secured and deployed the institutional and personal power resources identified by Heffernan to the domestic management of the Brexit process. It bears mention that despite treating these categories as distinct for reasons of analytical clarity, we do recognise their strong interconnection.

How did Theresa May and Boris Johnson compare in personal power resources?

Skill, ability, and reputation

Starting with an assessment of skill and ability, at the beginning of her premiership Theresa May employed this resource successfully, being capable of action on Brexit. She took over as prime minister at the beginning of one of the deepest political crises of modern times in the UK and her ability to step into leadership, stabilise her party (if only temporarily) and begin the Brexit process demonstrated effective crisis management. She managed to consolidate her position within the Conservative Party quickly, demonstrating the ability to mobilise support for her leadership. She also made several key appointments to her cabinet that indicated a clear strategic vision for her government's approach to Brexit, balancing different factions within her party. The poorly executed 2017 election campaign, however, exposed her leadership weaknesses and an inability to connect with voters (Heath and Goodwin 2017, p. 345). As shown below, the new circumstances (such as loss of her majority, the growing desperation of the Conservative Party, increased pressure from both rebellious MPs and opposition) constrained May’s ability to apply her leadership skills effectively, made her position more precarious and complicated her efforts to deliver Brexit. She never regained the political capital she had squandered. At the same time, she became increasingly impatient with anyone and anything that might potentially prevent her from carrying out her Brexit mission (Margulies 2019), further hindering her ability to effectively navigate the complex political landscape.

By contrast, Boris Johnson was able to use his personal abilities and skills more judiciously. May had sought to prevent him from becoming a veto player on the backbenches. She appointed him as Foreign Secretary, albeit while transferring responsibility for the government’s Brexit policy to the newly established DExEU (BBC News 2016). However, Johnson resigned in July 2018 over May’s Chequers plan. With this strategic move, he reinforced his reputation as a hardline Brexiteer supporting a ‘hard Brexit’. This consolidated the support of Leave MPs and party members, whose support Johnson needed to secure the party leadership (Ford et al. 2021; Russell 2022). Using his campaigning skills, he further bolstered his support among the 160,000 party members who selected the next Tory leader by stating that the UK would leave the EU on 31 October 2019 even without a Withdrawal Agreement (Ventura 2019). Upon finally reaching No. 10 Johnson was aware that he had inherited a precarious situation from May, but also that he had been elected chiefly on his promise to finally leave the EU—and quickly. So, his Brexit policy had to be delivered at any cost. Aware of his own limitations as a leader on policy and management he skilfully put together in No. 10 a “Brexit team which could be trusted, a team sufficiently radical and steadfast in the face of criticism. Where he as principal lacked resolve and grip, they would inject it” (Seldon and Newell 2023, pp. 70–71). Additionally, Johnson’s communication and public-speaking skills helped him to connect with a broad audience, which he could employ during the 2019 general election campaign helping to persuade 2016 Leave voters to vote now for the Conservatives. Moreover, Johnson was able to persuade the hardline-Brexiteers in his party, who had repeatedly obstructed May’s agreement with the EU, that “his” withdrawal agreement was worth voting for in Parliament and publicly supporting “as some sort of diplomatic masterstroke” (Bale 2020).

May was able to utilise her reputation as an asset, but only temporarily. In the first part of her premiership before the 2017 election she capitalised on being an “authoritarian persona”, and a reputation that combined being a “bloody difficult woman” with calmness and being a “safe pair of hands” that she had built up during her time in the Home Office (Kettle 2016; Worthy and Bennister 2020). Another element of May’s appeal was trustworthiness, with a long-cultivated reputation for blunt truth telling (Worthy and Bennister 2020, p. 11). Nevertheless, having broken her repeated promises not to call a snap election and then having failed to deliver the anticipated election majority, her reputation for trustworthiness and reliability was tarnished. Indeed, she came to be seen as incapable of delivering on her pledges and developed a reputation for being a fiasco prime minister, with her premiership increasingly defined by the Brexit catastrophe (Dunlop et al. 2020).

Johnson, in contrast, lacked May’s initially strong reputational assets in the early stages of his premiership. Before becoming Foreign Secretary, he had served as mayor of London from 2008 to 2016. His track record in both offices was mixed, though. While he had a high profile and was a well-known politician, he was also well known for controversial statements, both before but also during his period in office as Foreign Secretary (BBC News 2019a). Yet he had been a key figure in the Leave campaign in 2016 and, as described above, had cultivated a reputation as a hardline Brexiteer in May’s government. However, having managed to renegotiate the Withdrawal Agreement and gain a considerable majority in the 2019 general election (Uberoi et al. 2020) he earned the reputation of being a strong and dominant leader and, at the time, used it proficiently to his advantage. He did so, for instance, in relation to his cabinet. Johnson did not value dissenting voices in cabinet and dismissed Attorney General Geoffrey Cox and Northern Ireland Secretary Julian Smith in the February 2020 reshuffle. Both had criticised the government’s changes to the Northern Ireland Protocol during the Withdrawal Agreement renegotiation because of its implications for Northern Ireland. Their arguments were ignored, and both were replaced with individuals who were less critical and allowed Johnson to dominate his cabinet (Seldon and Newell 2023, p. 401).

Association with actual or anticipated political success

The two PMs also differed in terms of their association with political success. Johnson’s association was with Brexit success, May came to be associated mainly with the Brexit fiasco (Dunlop et al. 2020; Figueira 2022; Figueira and Martill 2021). Initially, there was anticipation that May would successfully get on with the job of delivering Brexit. The first part of May’s premiership witnessed little legislative dissent. She successfully steered the European Union (Notification of Withdrawal) Act 2017 through parliament within two months (Worthy and Bennister 2020, p. 13) and there was initially a widespread expectation that she would triumph in the 2017 general election. Yet, after the disastrous result and the repeated parliamentary rejection of her Brexit legislation, May’s association with political success evaporated and she came to be seen as a liability.

This contrasts starkly with Johnson. When he became prime minister in 2019, it was not clear that his hard line and apparent willingness to entertain a no-deal Brexit would be a more successful strategy than May’s approach to Brexit. He negotiated the Northern Irish Protocol by agreeing that Northern Ireland would continue to follow the EU’s rules and regulations on goods trade as well as its customs code to keep the border between Northern Ireland and the Republic open (Herszenhorn et al. 2019). Being able to claim that he had successfully renegotiated the agreement with the EU was an important asset for Johnson. His association with political success was further strengthened after the December 2019 general election. Johnson was able to exploit the success of being a highly successful election winner. Only Margaret Thatcher and Tony Blair had won larger majorities in the previous 50 years and the Conservatives moved from a minority government to their “first sizeable parliamentary majority… in a generation” (Ford et al. 2021, p. 551). By early 2020 Johnson was not only associated with the largest election victory for the Conservatives since Thatcher’s premiership, but also with taking Britain out of the EU.

Public popularity

It is our contention that neither PM could dependably draw upon personal popularity with the public as an asset. Public approval of and confidence in May’s premiership were associated with her handling of Brexit. Until the snap election, her approval ratings were very favourable and warranted her highly personalised election campaign. In early April 2017, after calling the election, her popularity ratings were “sky high”, reaching an impressive + 21% net approval rating (Helm 2017). Yet, post-election polls showed that 61% of voters viewed her in a more negative light than they had at the time of the election (Helm 2017; similarly, also Smith 2017). By early July 2017 her ratings plummeted to -20%. There have been only a few other cases in history when the public turned against a PM so rapidly (Helm 2017). In contrast, Corbyn experienced a diametrically opposite trend. In April 2017, his ratings sank to − 35%. However, by early June, he had surpassed May in popularity ratings for the first time, reaching + 4% in July (Smith 2017). Subsequently, the gap between the two narrowed, with Corbyn eventually seen again less favourably by the public than May towards the end of her premiership (Ipsos 2019).

In Johnson’s case, despite his high profile upon becoming prime minister, the public’s assessment was divided. Even after agreeing the Withdrawal Agreement with the EU, Johnson’s opinion poll ratings were not great: only 46% of voters were satisfied with him while 44% were not. In early December 2019, shortly before the general election, more voters were dissatisfied with him than were satisfied (36% satisfied, 56% dissatisfied) (Ipsos 2020). In fact, Ford et al. (2021) found that during the election campaign voters liked Johnson less than they had May during the 2017 campaign. The Tories’ “considerable leadership advantage” was due to Labour leader Jeremy Corbyn, who was even more unpopular than the Tory leader (Ford et al. 2021, p. 540). Throughout 2020, public dissatisfaction with the prime minister was often higher than satisfaction. Only in mid-March—at the start of the COVID-19-pandemic were a majority (52%) of voters satisfied with him, and 38% dissatisfied (Ipsos 2020). As was the case during the 2019 election campaign, however, Johnson remained more popular in comparison to Labour leader Jeremy Corbyn, who was replaced as party leader by Keir Starmer in April 2020. From June 2020 until the end of the year, Johnson’s net satisfaction ratings were continuously negative ranging from − 4% in August 2020 to − 31% in October 2020 (Ipsos 2020). Yet throughout the period considered here (June 2019 to December 2020) Johnson was continuously viewed by the public as more capable as prime minister than either Corbyn or Starmer (Ipsos 2022). Looking at this data, we conclude that Johnson was not able to draw on his personal popularity with the general public as an asset with regard to absolute popularity. Yet in terms of relative popularity vis-à-vis either Labour leader Johnson did benefit from opponents who at least during the early phase of his premiership were viewed as less capable prime ministers. That Johnson’s personal popularity in absolute terms was not great was also down to his divisive policies, particularly on Europe, and his persistent refusal to address the divisions between Remain and Leave supporters. However, his hardline approach on Brexit paid off, even if it made him unpopular with a section of Remain-supporting voters. He was able to unite the Leave voters behind his party in the 2019 general election.

High standing in the party

Whereas Johnson was able to successfully use his high standing in his party as an asset, May could not. She began her mandate with a small working majority of 17 seats but inherited a party deeply split on Europe and with a propensity for backbench rebellion (Lynch and Whitaker 2017, pp. 31–47). Still, May’s government remained undefeated in the House of Commons until May 2017 (Worthy and Bennister 2020, p. 13). Following the failure to secure a majority in the 2017 UK general election, she formed a minority government propped up by the Democratic Unionist Party (DUP). This reinforced her perceived weakness in the eyes of many in the Conservative Party. May’s concessions to the DUP left many unhappy as they felt it had compromised the government's bargaining position in the Brexit negotiations (Schnapper 2020). Divisions within the party became increasingly public, adversarial, and by June 2018, pathological. Between June 2017 and July 2018, her government suffered 13 defeats in the House of Commons and 30 defeats in the House of Lords (Worthy and Bennister 2020, p. 13). Her authority was further undermined by waves of ministerial resignations, with more than 30 ministers resigning over Brexit disagreements (Allen 2019). This diminished stature naturally reflected itself in the repeated failure to garner sufficient support from her own MPs for the Withdrawal Agreement. Importantly, the chief problem lay not only in the rebellions themselves but also in the resulting perception of weakness, chaos, and failure.

By contrast, Boris Johnson asserted his leadership over the party and successfully managed divisions and indiscipline early in his premiership. Here he was aided by the resignations of a number of moderate Tories who had served in May’s government and who rejected his no-deal policy (Pickard and Wright 2019). Then, in September 2019 Johnson withdrew the whip from 21 Conservative MPs who had voted against the government to prevent a no-deal exit (BBC News 2019b). At the time this, and his decision to prorogue Parliament for five weeks at the height of the conflict between the government and Parliament over it’s no-deal strategy, did not seem certain to be effective. However, ultimately both manoeuvres served to strengthen his authority over his party. A number of moderate and Remain-supporting MPs were removed as candidates for the Conservatives while others voluntarily decided against standing in the election (Payne and Hughes 2019). The result was to exclude those who fundamentally disagreed with Johnson’s approach to Brexit from the parliamentary Conservative Party in the new Parliament. In the short term, the Supreme Court ruled Johnson’s prorogation was unlawful (Bowcott et al. 2019). Yet, Johnson’s willingness to defy constitutional conventions in his determination to secure Brexit ultimately enhanced his standing and credibility in a parliamentary party which came to be dominated by Brexiteers.

How did Theresa May and Boris Johnson compare in institutional power resources?

Being the legal head of the government

Both prime ministers used the institutional power resource of being the legal head of government to attempt to secure their leadership over the government. Yet while they pursued similar strategies when it came to setting up their cabinets, these proved successful in Johnson’s case, but not so in May’s. In an effort to consolidate her power, May made a clear break with Cameron by dismissing several of his lieutenants and appointing her chief rival, Boris Johnson, to the Foreign Office in order “to trap him into collective and individual responsibility” (Allen 2017, p. 633). Yet, this strategy proved ineffective, as Johnson later played a significant role in her fall from power. His dissent over her Brexit strategy, public criticism of May, resignation from the cabinet and overt leadership ambitions undermined May’s authority and contributed to the perception of her weak and unstable leadership. May also reformed the institutional architecture of Whitehall to facilitate Brexit (especially by establishing two new departments: the Department for Exiting the European Union and the Department for International Trade). This antagonised the Foreign Office and the Treasury, as they were partially cannibalised in this process (Allen 2018, p. 113; Byrne et al. 2021, p. 709). Following the election, she managed to stay in office, but the rest of her tenure was marked by sustained pressure and a string of rebellions, crises, and the effective collapse of the cabinet government (Worthy and Bennister 2020, p. 9; Xu and Lu 2022).

Johnson, by contrast, was much more successful in using this institutional power resource. On becoming prime minister, he—like May—made a clear break with her government sacking about half of the members of her cabinet (while others had previously resigned on their own accord) (Pickard and Wright 2019) and giving key positions to leading Brexiteers, such as Dominic Raab (Foreign Secretary), Michael Gove (Chancellor of the Duchy of Lancaster), and Jacob Rees-Mogg (Leader of the House of Commons) (Stewart and Mason 2019). Johnson’s cabinet was “noticeably more hardline on Brexit” than May’s had been, as the Brexiteers in it supported a no-deal Brexit (Cowley 2021, p. 8). With this, the new PM also laid the groundwork for reshaping the Conservative Party, which after the 2019 election finally became “a party largely for and of Leavers” (Bale 2021). Johnson had little regard for his Cabinet, particularly after winning the 2019 election, kept it weak and ensured that ministers were unable to become too powerful and able to endanger his position (Seldon and Newell 2023, p. 459). Like May, Johnson made departmental changes. Once it was clear that Britain would finally leave the EU in January 2020, DExEU was abolished on 31 January 2020 (BBC News 2019c). Johnson tasked his former Europe advisor, David Frost, with the renegotiation of the Northern Ireland section in the Withdrawal Agreement and later the Trade and Cooperation Agreement. Frost had a special relationship to Johnson, as the latter “trusted Frost to negotiate with minimal input—he was the only person the PM intellectually deferred to in the team” (Seldon and Newell 2023, pp. 71–72). By delegating this responsibility to Frost, Johnson ensured that the management of the relationship with the EU remained under No. 10’s control instead of moving the Europe dossier (back) to the Foreign Office, for example.

Setting the policy agenda

For May and Johnson, Brexit policy overshadowed virtually everything else on the policy agenda. During the first part of her premiership, May’s hard Brexit strategy, announced first in October 2016, was a “powerful, if high risk, strategy of political radicalism” (Worthy and Bennister 2020, p. 5). During the latter part of her premiership, however, the very core of May’s Brexit policy vision came apart. Her radicalism changed into a “semi-cautious balancing act”, replete with constant shifts, changes, chaos, and gridlock. Her later compromises, especially on the Northern Ireland backstop in December 2017 and the Chequers Agreement in July 2018, pointed toward a softer Brexit (McConnell 2018, p. 173) and contradicted her earlier stance. This gave rise to significant bewilderment among politicians and the public alike, resulting in a lack of certainty about what May’s policy agenda on Brexit actually was.

Contrastingly, Johnson, having cultivated a hardline Brexiteer image, managed to decisively set the policy agenda on Brexit and Europe from the beginning of his premiership. He began during his leadership bid, when he announced that Britain would leave the EU at the end of October 2019, with or without a deal with the EU (Ventura 2019). His preference for a “sovereignty-first Brexit” (Grant 2020, p. 1), despite significant potential economic costs, became government policy. Until he secured the Withdrawal Agreement with the EU and won the December 2019 election, it was not clear that his hard Brexit rhetoric would amount to a tangible policy success. However, having reshaped the Tories to become a fully anti-EU party (Bale 2021), intra-party opposition on European and Brexit policy diminished significantly and the party more willingly followed Johnson’s agenda in the subsequent negotiation of the EU-UK Trade and Cooperation Agreement.

Organising a de facto prime ministerial department

Both prime ministers attempted to use to their advantage existing structures at No. 10 and in the Cabinet Office in their handling of Brexit. This was not a new pattern. Tony Blair, for instance, had attempted to extend his institutional resources with regard to European policymaking in a similar fashion (Bujard 2019, p. 109). As the civil service was, on Cameron’s instructions, unprepared for Brexit, in May’s case everything had to be decided on a running basis which further reinforced the significance of her own views. In September 2017, she streamlined Cabinet decision-making on Brexit and transferred the handling of the withdrawal negotiations to the Cabinet Office (Lloyd 2019, pp. 7–8). Control in the Cabinet Office was centralised in the newly created European Union Exit and Trade Committee which balanced those who had voted to remain with those who had voted to leave (Lloyd 2019, pp. 7–8). May’s working style was secretive and lacked openness, with strategic Brexit discussions and decisions kept within a small group of individuals she trusted, all of whom had limited experience in European affairs (Byrne et al. 2021, p. 710; Figueira and Martill 2021, p. 11). This elicited notable criticism from MPs about May’s “bunker mentality” and lack of access to decision-making on Brexit (Heide and Worthy 2019; Worthy and Bennister 2020). Despite replacing her aides with a new close group and de facto deputies after the snap election, her approach remained largely unchanged. This led to isolation and distrust among her wider team and the party, which undermined her centralisation efforts.

By contrast, Johnson, was willing to take personnel decisions which were highly unorthodox and were intended to disrupt the traditional functioning of No. 10 Downing Street. Despite lacking a parliamentary majority when entering office, he acted as if he was in a much stronger position. His appointments in Number 10 made no attempt to represent the varied voices in his party. On Brexit Johnson appointed only those who would support his hard Brexit strategy. He included key Vote Leave campaigners in his staff—most importantly the highly controversial Dominic Cummings, who became his chief advisor. While Johnson on paper set the government’s strategy on Brexit it was in fact Cummings who was driving it (Seldon and Newell 2023, p. 75). Cummings apart from providing the strategic and organisational planning Johnson himself lacked “was willing to operate outside of the conventional rules of politics and cross the lines Johnson’s aides wouldn’t” (Seldon and Newell 2023, p. 72). This is why the PM needed him to see his intended hard Brexit policy through. During the early stage of their collaboration, Johnson placed complete faith in him. Yet after the 2019 election their relationship became increasingly difficult, though Johnson had no intention at the time to find a replacement (Seldon and Newell 2023, pp. 75, 271). However, Johnson’s refusal to dismiss Cummings directly after the Barnard Castle incident of April 2020 would later damage him and Cummings only left No. 10 in November 2020 (Seldon and Newell 2023, p. 302). Additionally, with David Frost as Britain’s chief negotiator reporting directly to him, Johnson made clear that the relationship with the European Union was a priority and was being managed from Downing Street instead of delegating this task to his Secretary of State for International Trade, Liz Truss, or any other department, including DExEU (Stewart and Mason 2019; Mason 2020). What is more, Johnson’s stronger hold over his party early in his premiership enabled him to centralise power without facing the level of internal resistance that May had encountered.

Setting the government's political agenda through the news media

A PMs’ ability to set the government’s political agenda through the news media is closely tied to their communication and presentational skills. A prime minister who can communicate effectively, persuade convincingly, engage the public and manage their image well is likely to be more successful in exploiting this resource. Boris Johnson, as a former journalist and skilful campaigner, was much more accomplished in setting the media agenda than his predecessor. Until 2017, the news media, of which large sections were highly Eurosceptic and anti-EU, was generally supportive of May, helping promote the government’s line. Yet, May’s reliance on heavily controlled media appearances (Atkins and Gaffney 2020) and her poor communication skills and evasiveness (Brusenbauch Meislová 2019; Byrne et al. 2021, p. 712) (best exemplified by her infamous “Brexit means Brexit” tautology) undermined her credibility and weakened her leadership. What is more, her strong tendency towards repetition, which earned her the nickname “Maybot”, further eroded her image and made her a subject of ridicule. After the 2017 election, she entered a spiral of bad publicity, with the previously supportive media reporting widely on her weakness(es) (Kenny 2020). As a result, she struggled to take command of the media framing of the key Brexit issues.

Unlike May, Johnson very effectively used media management to set the government’s political agenda on Brexit. Slogans such as “Get Brexit Done” during the 2019 election campaign proved highly effective, because they persuaded enough voters on the Leave side “to see the election through the lens of their 2016 referendum choices” (Ford et al. 2021, p. 555). Johnson’s speeches were much reported, even although they included highly questionable statements. These included claims that there were “no non-tariff barriers” to trade in the Trade and Cooperation Agreement with the EU (Islam 2020) and, during the 2019 campaign, his suggestion that businesses affected by the paperwork required to trade in Northern Ireland should just discard it instead of filling it out (Russell 2022). While Johnson openly appeared to be economical with the truth, this did not turn out to his disadvantage, because it made good copy. At the same time, these kinds of remarks conveyed the impression that Johnson was willing to deliver on Brexit at any cost and spoke powerfully to Leave voters (and possibly to those voters who were tired of Brexit and just wanted to be done with it).

Discussion and concluding remarks

Using Richard Heffernan’s power resources model, the analysis has shown that Theresa May’s and Boris Johnson’s political leadership on the domestic handling of Brexit differed significantly and that the explanation for these outcomes does not only arise from a different political context and circumstances under which each prime minister pursued their Brexit policy. Rather Johnson, unlike May, made skilful use of the power resources at his command. He possessed more personal power resources and could draw on the available institutional power resources more effectively than May. Consequently, in the period until the end of December 2020 Johnson was able to be predominant in his political leadership on the domestic politics of Brexit, something Theresa May never achieved. In addition, we have found that although the different constituencies such as MPs, party members and voters clearly matter, a prime minister can be unpopular with several sections of these, but still be predominant.

Having used the Heffernan power resources model to compare the political leadership of Boris Johnson and Theresa May, we have encountered some of its limitations, based on which we now suggest two ways in which it can be revised. Firstly, we would suggest dividing the personal power resource “skill, ability and reputation” into two—with skill and ability as a resource distinct from reputation. While the skill and ability of a politician can be operationalised much more easily by examining the individual skill set of an incumbent, reputation is related to the perception by others of that office holder. Therefore, they should be analysed separately (as we did above) and not lumped together. The merits of this approach can be seen in the later stages of Boris Johnson’s premiership. While he attempted to legitimate his premiership mainly on his reputation of having “gotten Brexit done”, his limited skills and ability as a head of government (as opposed to a campaigner) contributed significantly to him being disposed of by his parliamentary party.

Secondly, Heffernan’s model fails to consider the relative importance of the various resources it outlines. As such, it risks oversimplifying the inherently dynamic, complex, and context-dependent nature of political power. Attempting to rectify this, in what follows we rank the power resources in a descending order of their relative importance, the most influential to those with less impact. This is not to diminish the role of any particular resource, but rather to acknowledge that they do not have the identical impact on a prime minister’s political leadership. Also, as Byrne and Theakston (2019) have noted, the various personal power resources feed into each other and—importantly in the context of ranking the various power resources of a prime minister—“it is only through possession of these personal power resources that the prime minister’s institutional power resources become truly effective” (332). Therefore, we will rank the personal power resources first.

Based on our analysis, association with actual or anticipated political success appears to be the most crucial personal power resource. It provides external validation that can be recognised by diverse stakeholders, including voters, party members and the media. Serving as a demonstration of a PMs’ skills and abilities, it typically enhances their influence within their party, improves their reputation, increases their public popularity and attracts additional resources that can further enhance their power and influence. The article has shown that May’s and Johnson’s differing associations with political success had significant impact on their respective handling of the domestic politics of Brexit and influenced what they were able to do in government.

Ranking second is high standing in the party which can enable PMs to achieve more political success, provide them with the necessary support to implement their policies and which, in turn, can enhance their reputation and increase their public popularity. At the same time, as an intra-party resource it may not necessarily translate into recognition or influence outside the party in the same fashion as actual or anticipated political success. This was particularly evident in May’s case, where her perceived weakness after the 2017 election and the subsequent dissension within her party severely undermined her intra-party handling of the domestic politics of Brexit. Conversely, Johnson could assert his authority and manage the divisions within his party by excluding dissenters instead of trying to accommodate them, thereby strengthening his leadership position.

Next is reputation which can directly influence a PMs’ standing within their party and their public popularity (and vice versa). Reputation is more subjective than the previous two personal power resources and can vary significantly depending on who is asked. It is also less reliable than concrete accomplishments or positions and more vulnerable to external effects. Initially, May had a strong reputation, but this was tarnished after the failed 2017 election and her inability to deliver Brexit. Johnson started with a controversial reputation but managed to renegotiate the Brexit deal and win a majority in the 2019 election, whereby he enhanced his reputation as a strong leader.

Individual skills and abilities are essential attributes for effective leadership, but they are not as influential as the previous three factors. This is because they must be demonstrated through successful political action to be recognised and valued. They often depend on other factors for their effectiveness, can be less directly translatable into power, and are more vulnerable to contextual changes. May initially displayed her skills and abilities effectively, but her subsequent leadership weaknesses and inability to navigate the political landscape undermined her perceived competence. Johnson, on the other hand, could leverage his skills and abilities to consolidate support and successfully steer the Brexit process.

The lowest-ranking personal power resource in our view is personal popularity with the public. We have found that it might not necessarily be an essential resource to enable a prime minister to be predominant. Heffernan initially developed his model during Tony Blair’s premiership. In hindsight, Blair enjoyed a very high degree of public popularity for a considerable length of time—something not experienced by any of his successors (Ipsos 2020). In addition, Heffernan initially defined a prime minister’s public popularity as “(l)eading a popular government, being personally popular as evidenced in consistently high, stable personal poll ratings, and successfully projecting a generally accepted ‘agreeable image’ through political marketing and political communication strategies” (Heffernan 2003, p. 353). While popularity relative to the Leader of the Opposition is needed for electoral success, high and stable personal popularity ratings might not be a necessity for a prime minister to be predominant. At least in the case of Boris Johnson personal popularity in the sense of absolute popularity was not an asset he could consistently draw upon. Yet he was lucky in his opponents, with the result that he was consistently viewed as the more capable prime minister in the period we analysed here. Nevertheless, as we have shown, despite his personal poll ratings he was still able to exercise predominant political leadership in his government’s Brexit policy. He was able to draw on the support of a specific segment of voters, and convinced Leave voters in larger numbers to support the Conservative Party in the 2019 general election. Therefore, public popularity—in the sense of absolute popularity as Heffernan has defined it—was not as crucial a factor as the others in the cases we analysed.

While we have ranked the personal power resources hierarchically, the nature of the institutional power resources is different. There is one resource, being the legal head of the government, that emerges as the most critical resource. It provides the prime minister with formal authority, the power to shape the government’s legislative agenda and the capacity to direct the machinery of government. As such, it is the institutional power resource that underpins all other institutional power resources Heffernan identified in his model. Both May and Johnson used this resource to restructure the cabinet and make strategic appointments. Yet, while Johnson was successful in consolidating his power and setting a clear direction for his government in the domestic handling of Brexit, May’s attempts to exert control led to discord and ultimately undermined her leadership. Given the crucial role of this institutional power resource, Heffernan’s remaining institutional resources are secondary to this and derived from it. The ranking that follows is therefore dichotomous and differentiates only between the main institutional power resource and the secondary ones.

Setting the policy agenda, although crucial, is dependent on this formal authority, and therefore a secondary institutional power resource. As we saw, the ability to set the policy agenda was dependent on the prime minister’s clarity and consistency in their policy stance. In contrast to May’s shifting attitudes on Brexit, Johnson’s clear and decisive policy agenda on Brexit allowed him to effectively mobilise support and shape the Conservative Party’s/government’s direction.

Setting the government’s political agenda through the news media is a supplementary resource to setting the government’s policy agenda. Without the latter a prime minister cannot do the former. While crucial in contemporary politics, its influence is less direct and more transient and is subject to external factors such as public opinion shifts and media bias. Johnson, unlike May, was particularly effective in this area. His ability to control the media narrative around Brexit played a significant role in shaping public perception and securing support for his policy agenda from significant sections of the public.

Organising a de facto prime ministerial department can be seen as another secondary institutional power resource derived from the PM being the legal head of the government. It can enhance the Prime Minister’s control over policy implementation and coordination among different government bodies, but its significance is conditional on the Prime Minister’s ability to effectively manage and delegate tasks within the department. The analysis showed that both May and Johnson sought to centralise control within No. 10 and the Cabinet Office, but the success of this power resource was dependent on their ability to maintain acceptance for the centralisation. May’s secretive working style led to criticism and erosion of trust within her party, which ultimately weakened her leadership. Johnson at the beginning of his premiership effectively placed a team in No. 10 and the Cabinet Office to implement the hard Brexit strategy he had set out during the leadership contest.

This being said, further analysis and comparisons of political leadership are needed to get a better understanding of the complex interplay between the various power resources and in how far the ranking of these resources based on the specific cases of Theresa May and Boris Johnson’s political leadership in the domestic politics of Brexit is in fact fluid or fairly fixed.