The notion that everyone is connected to everyone by a limited number of links has been around for ages, with John Guare’s film ‘Six Degrees of Separation’ as the most common popularisation of the concept. The increasing interconnectivity between individuals, combined with socio-political evolutions such as globalisation, leads to what Hungarian author Frigyes Karinthy originally refers to as ‘a shrinking world’ or what American psychologist Stanley Milgram calls a ‘small world evolution’. American social scientists James H. Fowler and Nicholas A. Christakis designed a more systemic and explanatory theory referred to as ‘three degrees of influence’, which indicates social networks have a potential to influence individual behaviour and their influence goes beyond the individuals we know. Even though individual behaviour is the theory’s primary scope, it is systematically applied with different outlooks and in a wide variety of scholarly fields.

For example, in a far right party (FRP) context - while considering FRPs as rational agentsFootnote 1, this implies FRPs are likely to influence one another and the resulting linkage between them is more extensive than just direct and visible ‘nodes’ (to use SNA analogy). Per this theorisation, FRPs form a complex network, which is not surprising considering they are a party family [44, 60]. Consequently, one can ask two paradoxical questions, both treated in this critical reflection. First, if such relations appear unmistakable and are embedded in theory, why does the majority of FRP research not account for them? Second, if the connections between FRPs indeed play an important role, how is it possible to further define and analyse this role, particularly in the specific context of FRP development and/or success?

This critical reflection seeks to clarify and elaborate the enigmatic nature of these questions. It also advocates for a more detailed analysis of the dynamic FRP network, irrespective of the fact that the study of interdependence is relatively uncommon in party politics and largely absent from FRP research. Furthermore, and based on those initial arguments, this critical reflection recognises the role of interdependence and argues for its inclusion in the explanatory framework of FRP development. These theoretical arguments are supported by a number of empirical illustrations.

The broader literature: Interdependence as a systematic hypothesis

In the academic literature, the study of interdependence is quite extensive and embraces a widespread applicationFootnote 2. The Treaty of Westphalia (1648) resulted in the European-wide dispersion of the territorially bounded nation-state [40]. Participatory democracy finds its initial foundation in the French Revolution [9]. The third wave of democracy globalised the Carnation revolution in Portugal [30]. In the United States, political communication experienced a paradigm shift, which subsequently spread to and throughout most of the Western world [55]. Since the 1980s, regulatory capitalism has been gradually spreading from North to South [43].

The dynamics that describe these different expressions of interdependence comprise the dissemination of a specific object between socio-political entities or contexts, at a particular time and via a variety of networks. The theorisation and inclusion of these dynamics can add validity and precision to some of the broader, yet more rigid and spatially limited explanatory frameworks. Given this understanding, some of the recent social movement literature appears to focus on the systematic linkages between spatially and temporally proximate movements.

Tarrow’s notion of cycles of protest indicates that certain pioneering movements provide (other) protest groups with tactical, organisational and ideological ideas for their protest [69, 70]. della Porta and Rucht introduce the concept of movement families and thereby emphasise the association between them [17]Footnote 3. They both provide evidence of a certain level or form of interdependence between movements within the same sociopolitical context. Yet, interdependence must not be restricted to the same socio-political setting. An important example of such trans-national linkages is the revolutionary wave throughout Europe in 1,848 or the student protests in 1968. In short, numerous social movement scholars advocate for the inclusion of the international origins of social movements [46] and their trans-national visions [62].

Similar analyses of interdependence can also be found in party politics. Several studies indicate the spread of communist attitudes and support, both within and between socio-political contexts, as early as the 1920s [6, 39, 26]. Furthermore, studies have been published on inter-party cooperation in Scandinavia [2, 36], policy coordination between Christian democratic parties [35], the developmental cooperation in the post-communist world upon its transition away from Communism [77], the competition between right-wing parties for issue ownership of Euroscepticism [65], the cooperation between social democratic parties [42], trans-national cooperation between European green parties [18], general cooperation in the European Parliament [4, 41, 72], the transnational cooperation between extreme right parties and movements in Eastern Europe [45], and even the cooperation between post-communist and nationalist parties in Eastern Europe [33]. Most recently, scholars come to assume that FRPs play an important (causal) role in the right turn of European politics [54]. This proposed Verrechtsing or droitisation hypothesis is still underdeveloped, but regardless of its disputed validity and spurious evidence, the potential influence FRPs have on different aspects of society is becoming the subject of a growing body of researchFootnote 4.

The general awareness of diverse forms of interdependence throughout different literatures yields several critical considerations. Seeing how interdependence and trans-national linkage are frequent and important subjects of analysis in political science subfields like international political economy [37] and public policy [64], why is it not possible to find a similar appreciation in the FRP literature? Why are interdependence and patterns of trans-national influence between FRPs not incorporated in explanatory frameworks of FRP development? More specifically, given that extensive theorisations exist regarding FRPs’ influence alongside different socio-political dimensions of politics, why is research on their trans-national interdependence largely deficient?

The FRP literature: independence as a systematic hypothesis

Throughout the literature, there is little conformity or consistency regarding the terminology and the conceptualisation used to refer to this party family. Yet, the proposed terminology does not have internal ideological contradiction or inherent history that might change its implicit connotation. In addition, the term FRP represents simplicity and is relatively uncomplicated, which the current literature often undervalues.

Its conceptualisation is based on three broad criteria: a spatial, an attitudinal and a systemic criterion. The spatial criterion refers to the party’s positioning to the right of (most) traditional parties, but to the left of undemocratic and anti-system parties. Since the position of each party changes through time and between socio-political contexts through their dependency on demand side factors, supply side factors and the interaction with other parties, it is difficult to standardise this relative distance. Two additional principles contribute to a more exact conceptual placement of FRPs. On one hand, an attitudinal component describes the core political values FRPs propose, most crucially in the form of nationalism, xenophobia, and authoritarianism. On the other hand, a systemic component describes how and to what extent FRPs oppose the ambitions of the societal system and its principal agents (i.e. traditional parties and existing elites). This notion of goal differentiation to criticise, yet remain loyal to the existing system can be described by another core characteristic of FRPs, namely populism [73].

Implicitly or explicitly, most research assumes FRPs to be independent from one another, particularly throughout their life cycle. On one hand, the assumption of FRP independence facilitates the composition of separate cause-and-effect models of FRP development. Often, the literature either perceives FRPs as inward-looking and highly conservative agents, or it discerns (developmental) similarities as independent responses to common or similar challenges, without any sort of interdependent process or influence between FRPs [3]. On the other hand, some analyses do allow FRPs to be interdependent entities and for their development to be an interdependent process, yet most of those studies do not scrutinise such a stipulation any further [52]. In those cases, the specification of interdependence takes the form of an assumption, rather than a hypothesis or a subject of analysis.

Hence, it is difficult to dispute that the existing FRP literature often overlooks interdependence. It disregards how FRPs affect one another across national boundaries and how prior choices in one socio-political context can influence posterior choices in another socio-political context (cf. Bayes’ theorem). This implies FRP literature can be described as systematically biased in favour of a state of structural independence between FRPs. In other words, most analytical accounts of the FRP phenomenon (regardless of their scope) rely on a hypothesis of developmental independence, either in the form of a simplifying assumption or an unspecified theorisation.

Structural independence as an unlikely hypothesis

A number of preliminary observations suggest the FRP independence hypothesis might not be as likely or even plausible as commonly assumed. The increasing salience and widespread character of globalisation interconnects socio-political contexts and agents in disparate locations [16]. The growing presence and importance of globalisation indicates that (electoral) mobilisations in different socio-political contexts are rarely isolated and independent from one another [47, 24]. As part of the paradigm shift/s in political communication, several socio-political evolutions have contributed to the international character of modern media, its attributes and effects [55]. To list but a few, such dynamics shape FRP behaviour (their decision-making procedures) and influence their development; yet, they remain systematically underestimated by the existing literature. In theory, FRP independence is possible and FRP similarities can be the result of random and unforeseen dynamicsFootnote 5. It would indicate these FRP similarities - notably in their developmental patterns - are either accidental or a direct consequence of similar external challenges, which then leads to similar outcomes at similar times. Considering the extensive similarities between FRPs (most notably their shared master frame and their ideological components), this would be an unlikely coincidence. Moreover, since FRPs are (conservative) change agents Footnote 6 and following the above-described societal evolutions, it would be rather implausible to assume FRPs seek to maximise (political or electoral) utility and cease to look for information at their national borders [12, 79]. In short, it would be more accurate - even realistic - to think of developmental independence as an unlikely and implausible hypothesis.

Despite their consideration as a party family and a number of developmental similarities between them [44, 60], FRP development is not a continuous process and one can observe significant heterogeneity between FRPs (e.g. developmental pathways, electoral power, media strategies, governmental participation). In the existing literature, these differences between FRPs are most often attributed to supply side factors, which also allow for an indication that independence can be questioned. More specifically, spatial and temporal heterogeneity can be considered outcomes of an overarching process (such as interdependence) that allows for procedural variation in its operation by the application of a unique set of underlying mechanisms and principles.

von Beyme substantiates this by suggesting that FRPs are but the most recent wave of post-war right-wing extremism [76]. In other words, FRPs are but an episode within a larger phenomenon. Such an interpretation is quite similar to Tarrow’s argument of the cyclical nature of contentious politics [71]. He acknowledges that interdependence is an important foundation of any cyclical phenomenon [28], which would indicate that interdependence between FRPs is crucial in their developmental trajectoriesFootnote 7. Within each wave, the specific dynamics that explain a trend between agents are more complex than shared responses to external circumstances (i.e. demand side factors) or coincidence. Hence, it is essential to expand the scope of the existing framework that describes the development of an FRP within such a wave.

The incongruence between existing theorisations and assumptions on one side and pragmatic and empirical observations on the other provide an initial signal that the structural independence hypothesis and the present accounts of FRP development should be revisited. The independent analysis of FRPs is not accurate, nor realistic and ignores certain conditionalities and external dependencies (cf. Galton’s problem)Footnote 8. Most often, this dilemma is simply ignored [8] or neglected [14] so one does not have to deal with the potential difficulties it brings (e.g. correlated error terms, biased standard errors).

To the best of the author’s knowledge and abilities, only three existing studies take into account the potential interdependence between FRPs. Husbands recognises that FRP support levels appear in waves - confirming von Beyme’s original contention -and are partially caused by ‘contagion’ [31]. DeClair models explicit trans-national links between the far right’s mother party - the FN - and other FRPs [15]. Thus far, Rydgren has published the most comprehensive effort. He proposes the inclusion of FRP interdependence upon explaining their emergence and he does so by referring to these dynamics as patterns of diffusion [60].

These existing research efforts are admirable and serve as initial incentives to go further and resume scientific developments. This critical reflection contributes to the debate by providing an indication of the unlikely nature of the independence hypothesis, and aspires to stimulate future research to explicitly and formally incorporate interdependence between FRPs as part of the explanation of FRP development. In an effort to analyse FRP development more accurately and comprehensively, this study proposes that any and all analytical accounts of FRP development should not be restricted to the analysis of independent FRPs or an autonomous phenomenon, but should also include trans-national dynamics. Furthermore, this critical reflection implies such dynamics can most accurately be described by trans-national diffusion patterns.

Introducing interdependence: trans-national diffusion dynamics

The described interdependence between FRPs is most appropriately defined as, “the acceptance of some specific items, over time, by adopting units - individuals, groups, communities - that are linked both to external channels of communication and each other by mean of both a structure of social relations and a system of values, or culture” [38, p.78] and can be termed trans-national diffusion. This particular definition gives the concept of diffusion exceptional explanatory power, while defining four distinct components: (i) agents (a transmitter and an adopter), (ii) an object or innovation, (iii) mechanism/s, and (iv) channel/sFootnote 9.

Put differently, trans-national diffusion is a process by which a certain innovation (the object) is communicated from one FRP (the transmitter) to another (the adopter) through certain channels while using certain mechanisms. Its principal agents - here, FRPs - are participants in a social system, requiring some initial association between one another. The mechanisms and channels of diffusion comprehensively model how trans-national diffusion between FRPs materialises. Even though diffusion most often describes individual-level research, Rogers indicates, “(…) it seems reasonable to expect that experience with the innovation is gained as each successive member in the social system adopts it. Each adoption in the social system is in a sense equivalent to a learning trial by an individual” [58, p.44].

Specifically, three decisive observations confirm the pertinence and accuracy of the notion of diffusion in the proposed context of FRP development. First, since the 1980s, an increasing number of FRPs share specific resemblances along different dimensions (ideology, strategy, communication, appearance, etc.), eventually resulting in trans-national similarities between these parties. As indicated earlier, it is highly unlikely they are the sole result of simultaneous, yet independent developments. Following the societal evolutions described earlier, trans-national communication and influence patterns are systematic in any party’s development. Second, it is possible to distinguish the FN as somewhat of a defining party for this particular party family, often referred to as a ‘pater familias’ [5, 32, 51, 60]. This suggests the FN serves as an important source of FRP similarities, which is confirmed by its status as an important innovator and transmitter. Third, FRP development is not a continuous (linear) process but rather a dynamic process that allows for spatial and temporal heterogeneity. As a function of time, FRP development can be described by an S-shaped cumulative curve [57, p.273, Fig. 7.1]. This latter argument is perhaps the principal indicator why FRP interdependence can be - and should be - termed and conceptualised as (trans-national) diffusion.

Social mechanisms vs. variables

Rather than designing situational structures with limited external validity or universal theories that can explain everything, a framework that includes diffusion dynamics as an imperative analytical construct provides a compromise between the two. Hedstrøm and Swedberg suggest social mechanisms - like diffusion - can cover the middle ground between social laws and description by stipulating a systematic account of how cause-and-effect are linked to one another [29]Footnote 10. An important advantage of this approach is the ability to provide a more comprehensive and multi-dimensional account of a phenomenon by the analysis of how a (causal) relationship is constructed. In short, this critical reflection suggests future research should examine the validity and complexity of trans-national diffusion patterns between FRPs by going beyond simple cause-and-effect models and by including social mechanisms as an important construct of the explanatory framework of FRP development.

Some of the existing explanatory frameworks of FRP development are restricted in their scope to either the explanation of FRP similarities (demand side) or some of their more prevalent differences (supply side). Only on rare occasions are both approaches combined and are frameworks able to explain patterns of variance, i.e. both similarities and differences. The integration of trans-national diffusion as a social and explanatory mechanism would not only complement the more structural and variable-oriented accounts of FRP development, but it would also provide a more comprehensive (explaining both similarities and differences) and dynamic (including processes in addition to variables) explanatory framework of FRP development.

Trans-national diffusion patterns between FRPs

This paper suggests that the existence of trans-national diffusion patterns between FRPs, notably as part of their developmental process, is more likely than typically assumed throughout the literature. Even more, its identification and insertion in an explanatory framework appears both reasonable and realistic. Notwithstanding this pragmatic observation, the feasibility of both a formal theorisation and a practical observation of trans-national diffusion remain underdeveloped. Therefore, in support of future research,

The unlikely independence: FRP similarities

At the outset of any (political) analysis, it is essential to actually recognise and identify trans-national diffusion as such. It is possible to make three observations that provide initial evidence of trans-national diffusion dynamics between FRPs and give a primary indication of the role diffusion dynamics play in the FRP development process.

As already indicated, it is possible to interpret FRPs as a recent expression of right-wing extremism [76], which makes it part of a larger cycle-like phenomenon of contention [71]. It would be highly unlikely to propose that numerous simultaneous expression of right-wing extremism are accidental (i.e. independent) and do not share either common characteristics or collective origins. Second - and directly following this, it is also possible to observe a number of trans-national developmental trends or similarities within each wave, most notably of their master frames, ideological components and strategies. Different forms of (routes to) success and failure - and notably their causes - are observed and taken into account by fellow FRPs. The subsequent similarities increase the social proximity between FRPs and connect them as a party family, thereby making diffusion between them all the more likely. Third, the lack of simultaneous adoption of the previously mentioned similarities indicates some form of spatial and temporal heterogeneity as part of this discontinuous process.

Particularly the extensive FRP similarities are an important reason for the pragmatic rejection of the structural independence (or myopic diffusion) hypothesis. A decisive source of similarity and potentially one of the most important objects that travel between FRPs is undoubtedly of an ideological nature, more specifically, the FRP master frameFootnote 11. The pre-1980s master frame (as used and implemented by first- and second-wave right-wing extremist parties) lacked electoral appeal; thus, spatial modelling indicates a ‘new’ master frame became indispensible. Given that only few FRPs have the intellectual, financial and substantive resources to design a new and innovative master frame, the FN is widely perceived as the primary innovator of the master frame most (West-European) FRPs still share today, which, in its turn, is often understood as the foundation of their initial electoral success and eventual emergence. Shortly after the FN’s initial successes in the early and mid-1980s, several risk-seeking parties adopted a master frame similar to the FN’s. Throughout the 1990s and the early 2000s, this was followed by a larger majority of FRPs also adopting such a similar master frame. Since then, a small number of smore risk-averse adopters also implemented the FN’s master frame. Graphically, these different adoption categories, combined with their times of adoption, can be depicted by an S-shaped (logistic) cumulative adoption curve. In short, through trans-national diffusion as a social mechanism, this ‘new’ master frame plays a crucial - perhaps even indispensable - role in the initial development of FRPs.

The similarities between FRPs, as well as the conditionality through time and space, support an FRP trend throughout Western Europe. Not only does this stimulate the recognition of trans-national diffusion between FRPs, it also validates the relevance of these dynamics as part of FRP development. Given the overall identification of diffusion patterns, it is then possible to further stipulate the specificities of this process.

Since patterns of diffusion are - by definition - spatially and temporally heterogeneous, the roles as transmitter and adopter are not necessarily fixed throughout an FRP’s development. Furthermore, it is necessary to make three specifications regarding the role of FRPs throughout the diffusion process. First, whereas a transmitter can be passive, an adopter cannot, which implies adoption (the receiving process of diffusion) is always conscious and perceived desirable (i.e. utility-maximising). Second, the social distance between FRPs plays an important role in the diffusion process. Specifically, it is possible to hypothesise that a provision of social proximity between FRPs not only facilitates (i.e. optimises) diffusion, but also is necessary for it to be persistent. Third, upon adoption, an FRP serves best to properly align the object of diffusion to its socio-political context so as to increase its likelihood of direct success.

The two most prevalent courses of frame alignment in an FRP context are frame bridging and frame amplification. Frame bridging allows an FRP to link previously unconnected master frame components so as to expand its potential audience. Often times, FRPs divide the electorate in two antagonistic groups with their dualistic frames. Nationalism does this by creating those within and outside the nation. Populism differentiates between ‘the people’ and the ‘elite’. Authoritarianism differs between those who submit to and those who reject authority. Xenophobia emphasises fear of ‘the other’. In this context, it is advantageous for FRPs to generate overlap between several of these antagonistic categories, thereby bridging different audiences. Frame amplification indicates that certain master frame components take priority over others. Because these components are often directly and most concretely linked to the electorate, this process reduces ambiguity and increase consideration for the (entire) FRP master frame. This is mostly achieved through rhetoric (about immigration, the EU, etc.) and is a particular strength of FRPs.

FRP development and the process of diffusion

After the more detailed description of the ‘whom’ and the ‘what’ of trans-national diffusion between FRPs, it is possible to theorise the more complicated ‘how’ of trans-national diffusion between FRPs by describing its mechanisms and channels. Their breakdown allows for a more dynamic and comprehensive account of FRP development, while also incorporating heterogeneity and allowing for a certain level of generalisation.

FRPs adopt an alternative master frame based on the underlying logic of a (utilitarian) threshold, i.e. an FRP will only adopt a new master frame if it is beneficial. This suggests the interpretation of other FRPs’ experiences has a conditional effect on the diffusion process and its mechanisms, as illustrated by changes in the relative effectiveness and payoffs associated with a new master frame [11, 75]. Based on the diffusion literature, it is possible to distinguish two particular mechanisms most prominent in describing trans-national diffusion between FRPs: Emulation (or imitation) and learning. The former does not require an active transmitter, whereas the latter does. As change agents, FRPs can develop and emphasise different aspects of a master frame and a diffusion process, depending on which party objectives it considers imperative. Specifically, emulation largely influences diffusion through a master frame’s relative payoffs, whereas learning primarily influences a master frame’s relative effectiveness. Through either one of these mechanisms, an FRP seeks to acquire information (e.g. a master frame) from another context and apply it to its own context, with the primary perspective of contributing to its successful development.

The conditions under which these subjective interpretations are transmitted between FRPs can be divided into two dominant, yet non-mutually exclusive diffusion channels: Interpersonal and impersonal. Interpersonal channels mostly refer to different forms of face-to-face (direct) interaction and communication, without an intervening entity to guide the information flow. Impersonal channels are more complex because there is a third agent guiding the information that travels between FRPs. These intervening agents are diverse in nature, but often times this third agent is some form of mass media. Since this limits the opportunities for (direct) interaction and communication, impersonal channels typically impede organised and more structural forms of diffusion. It is through these combined channels FRPs inform themselves on how they can most efficiently adopt (or reject) certain changes they observe in other national contexts in order to effectuate successful party development.

A brief illustration of trans-national diffusion between FRPs

It is possible to further illustrate trans-national diffusion between FRPs, and provide an initial account of how this framework can contribute to a more accurate and comprehensive theorisation of FRP development. As part of a larger on-going research project, this critical reflection relies on a number of semi-structured interviews with politically knowledgeable subjects. More specifically, the researcher uses 49 in-depth interviews, nearly all of which (43) constitute elite interviews from 11 different FRPs: the FN, the MNR, the VB, the FNb/DNb, the FPÖ, the REP, the BpD, the BNP, the PxC, the LN and the SD. Within this sample, 21 interviews have been conducted with high-ranking party officials and 22 with non-political, yet prominent functionaries.

Without committing to an exhaustive and overly detailed analysis, it is possible to draw some broader conclusions from this data collection process. Most importantly, all interviewees - without exception - recognise the importance of other FRPs in their development, as well as the explicit and often formal attention they give to the developments of FRPs in other countries. It also appears this attention is mostly positive, as successful FRPs are extensively highlighted, while some of the more cautious tales often remain silent or even undisclosed. Even though trans-national diffusion is overly present throughout the FRP history, it also appears to be closely linked to individuals, and perhaps even the interpersonal skills of some of the high-ranking FRP officials. In support of this critical reflection’s proposed importance of trans-national diffusion as an explanatory dynamic of FRP development, it was also properly recognised that in addition to diffusion’s more restricted interpretation as a between-FRP dynamic, its wider interpretation also plays an important role in FRP development. The diffusion patterns with other domestic parties, as well as with both more traditional and more extreme parties in further-away contexts, are typically also identified as contributing factors to the FRP development.

Based on the policy diffusion literature, it is possible to theorise learning as a more complete and all-encompassing mechanism, with particular benefits for an agent’s long-term development. In an FRP context, this hypothesis can be initially substantiated by empirical evidence. FRPs that have used learning mechanisms and interpersonal channels as a foundation of their trans-national diffusion dynamics all seem to have experienced successful emergence. Those that systematically continue to do this after their emergence appear to have consolidated and develop into successful political parties (e.g. FN, VB, SVP, LN, etc.), whereas those that did not uphold ‘learning’ failed to (or have yet to) consolidate into a systemic political presence (e.g. REP).

The policy diffusion literature also allows for the theorisation that emulation and impersonal channels would appear to contribute positively to initial FRP development, as it introduces an FRP to the FN’s new master frame and it allows an FRP to take advantage of the potentially increased payoffs that come with this master frame. More broadly speaking, it is possible to hypothesise that emulation has the potential to serve as a foundation for more structural forms of trans-national diffusion. However, the signals that could provide some preliminary validity to these hypotheses remain rather spurious. Initial evidence substantiates that emulation can serve as a partial instigator of FRP emergence and a potential foundation for future learning mechanisms (e.g. BZÖ, PxC, BpD). Yet, for several FRPs these opportunities for more matured and interactive forms of trans-national diffusion dynamics did not necessarily prove successful (e.g. CD, BNP, FNb/DNb). Therefore, it is clear that trans-national diffusion cannot serve as a sole explanatory factor for FRP development; rather, it must be understood as only one piece of the ‘explanatory puzzle’.

Social distance plays an important role throughout the diffusion process. Originally, there was no FRP family, as there was nothing that served as a structural link between these parties. Yet, the initial success of the FN’s new master frame led to trans-national diffusion of that master frame, eventually resulting in FRP similarities and increasing social proximity between these parties. The reduced social distance between FRPs subsequently increases the likelihood of the development of more structural interpersonal networks, accompanied by comprehensive learning mechanisms.

Regardless of the possible implications of these observations, the evolution of diffusion mechanisms and channels is not as gradual - or linear - as could be assumed. It is important to make two additional specifications to provide a more accurate account of trans-national diffusion patterns. First, it is quite possible, and even likely, that different trans-national diffusion channels operate simultaneously. Therefore, it is imperative to specify that both channels and mechanisms of diffusion complement, rather than supplement one another. Second, the existence or use of one particular channel does not preclude or exclude the existence or use of another. Moreover, the development of one can enrich and/or reinforce the other. Much like the FRPs themselves, one can argue diffusion channels (and mechanisms) to be interdependent.

Prospective remarks

The hypothesis of developmental independence between FRPs is widely used throughout the FRP literature as a silent presumption, most often due to the absence of a comprehensive or appropriate analytical framework that can include interdependence. Founded on both theoretical and pragmatic motivations, this critical reflection explicitly argues for the rejection of such a hypothesis. In addition, this paper provides an initial applied account of the proposed interdependence between FRPs (here defined as transnational diffusion), thereby justifying and validating such an approach.

Existing accounts of FRP development are often partial and relatively static in nature, while they often overemphasise the explanatory value of certain variables (e.g. the level of immigration). The introduction of trans-national diffusion as an explanatory dynamic transcends and complements existing explanations, while also acknowledging and incorporating the interdependent disposition of the FRP paradigm.

With this proposed inclusion of trans-national diffusion dynamics, it is then possible to revisit or propose a number of perspectives that should serve as objectives of upcoming research endeavours. Most importantly, it is crucial to first examine whether trans-national diffusion between FRPs occurs as such, and preferably as part of a more systematic effort. Keeping in mind diffusion’s four critical dimensions, one should further analyse these dimensions. Who are the agents in this particular trans-national diffusion process, what are their characteristics that can facilitate or impede trans-national diffusion patterns, and how do their roles vary throughout their life cycle? What exactly are the objects of diffusion, what role do they play in the development of a party, what exactly influences an innovation’s effectiveness and payoff, and to what extent do the innovations need to be aligned with a specific socio-political context? How do the different mechanisms and channels influence diffusion and its potential success, what are the primary factors at the origin of the proposed conditionality, how exactly do these mechanisms and channels influence FRP development, and (how) is it possible to include these dynamics in a formal model of FRP development?

In addition to these more ‘descriptive’ questions, a number of ‘why’ questions should also have a place in future research. Why does a particular object diffuse in favour of another object? More specifically, why has the FN’s proposed master frame served as an inspiration for so many FRPs, and not one designed by another FRP? But also more generally, why does trans-national diffusion between FRPs take place at the time it does? These questions - and so many other ‘why ‘questions in social science - are notoriously difficult to answer because of the inherent difficulty of social science to provide complete and comprehensive accounts of the intentions and experiences involved in a widespread phenomenon like trans-national diffusion between FRPs. Nonetheless, regardless of its complexity, future research should not avoid these questions.