Abstract
Since the mid-twentieth century, elite political behavior in the United States has become much more nationalized. In Congress, for example, within-party geographic cleavages have declined, roll-call voting has become more one-dimensional, and Democrats and Republicans have diverged along this main dimension of national partisan conflict. The existing literature finds that citizens have only weakly and belatedly mimicked elite trends. We show, however, that a different picture emerges if we focus not on individual citizens, but on the aggregate characteristics of geographic constituencies. Using biennial estimates of the economic, racial, and social policy liberalism of the average Democrat and Republican in each state over the past six decades, we demonstrate a surprisingly close correspondence between mass and elite trends. Specifically, we find that: (1) ideological divergence between Democrats and Republicans has widened dramatically within each domain, just as it has in Congress; (2) ideological variation across senators’ partisan subconstituencies is now explained almost completely by party rather than state, closely tracking trends in the Senate; and (3) economic, racial, and social liberalism have become highly correlated across partisan subconstituencies, just as they have across members of Congress. Overall, our findings contradict the reigning consensus that polarization in Congress has proceeded much more rapidly and extensively than polarization in the mass public.
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Notes
Lest this possibility seem merely hypothetical, consider the classic finding that for much of the twentieth century, Democratic states had more conservative policies than Republican States, despite the fact that within every state Democratic officials were more liberal (Erikson et al. 1989; Caughey et al. 2017).
We obtained Senate roll call data from voteview.com and assigned roll calls to issue domains using the issue codes provided by the Policy Agendas Project (Adler and Wilkerson 2017).
We used the R package MCMCpack (Martin et al. 2011) to estimate the ideal points. To reduce computation time, we sampled 100 economic roll call votes in each congress. For the social and racial ideal points, we used all available roll calls (which always number fewer than 100 per congress). For a discussion of how dynamic IRT estimates differ from DW-NOMINATE scores, see Caughey and Schickler (2016).
It is important to note that the estimates of intrastate ideological divergence in the Senate plotted in the top panel of Fig. 1 are based on split-party delegations. However, the mix of states with split party delegations has fluctuated over time (Brunell and Grofman 2018). Thus, some of the flux in intrastate ideological divergence in the Senate in Fig. 1 could be due to changes in the mix of states with split-party delegations. We have used two approaches to assess how much changes in the mix of split party delegations affect our analysis in Fig. 1. First, we have replicated the analysis in Fig. 1 separately for Southern and non-Southern states. We find similar patterns across regions, which suggests that changes in the regional mix of split party delegations only have a small effect on our estimates of partisan polarization in the Senate. Second, we have replicated the analysis of the Senate in Fig. 1 using a model that includes fixed effects for each state. This analysis purges the effect of changes in the mix of states with split party delegations by isolating the within-state trends in divergence. This analysis too shows very similar patterns as in Fig. 1.
Trends in intrastate divergence as measured by first-dimension DW-NOMINATE scores look similar to those as measured by our economic ideal points. In particular, according to both measures intrastate divergence in the contemporary Congress is about two standard deviations. This makes sense since the primary content of the first dimension has historically been economic issues (Poole and Rosenthal 2007). The main difference between the two series is that according to DW-NOMINATE, the post-1960 decline in intrastate divergence persisted longer, and the subsequent increase occurred later and less gradually than our economic ideal points imply.
Our preliminary analysis indicates that online surveys, such as the Cooperative Congressional Election Studies, show more polarization and sorting than phone surveys. Thus, we omit online surveys in order to ensure the inter-temporal comparability of our results.
We coded the polarity of questions based on the substantive valence of the question. For example, for economic questions we examined which response option implied a larger scope and size of government. We generally dichotomized multichotomous questions around the middle category.
Our aggregate-level data limit our ability to evaluate how much these developments were driven by changes in the demographic composition of the parties versus changes in individual issue attitudes. We suspect, however, that both factors were at play. We know, for example, that in the 1960s African Americans, who were and continue to be much more racially and economically liberal than whites, became much more likely to identify as Democrats (e.g., Petrocik 1987). This compositional change, along with conservative Southern whites’ more gradual countervailing shift toward the Republican Party (Green et al. 2002, pp. 140–163), likely explains much of the increase in divergence in Southern states, especially on racial issues. On the other hand, we also know that at least some of the growth in polarization is due to individuals’ changing their issue attitudes to match their party’s positions (Levendusky 2009a; Lenz 2012), and thus intrastate divergence is likely also a product of the changing issue attitudes of individuals who remained loyal to one party.
Specifically, within each biennium, we used analysis of variance to decompose variation in conservatism across senators/subconstituencies into between-party and within-party components. The proportion of variation explained by party is simply the between-party sum of squares divided by the total sum of squares.
In addition to being a period of unusually low partisan polarization, especially in presidential politics, the 1950s were also a dry spell for survey questions that tapped into ideological differences over economic policy (see Erskine 1964, pp. 154–155). Both factors may help explain the sudden drop in the explanatory power of party in this decade.
Carmines and Stimson’s analysis was based primarily on a handful of ANES questions. In contrast, we use nearly all available data on public opinion about race during this period from 46 question series across 73 polls.
This too is consistent with the analysis of first- and second-dimension NOMINATE scores in Poole and Rosenthal (2007).
See Hopkins (2018) for a detailed description of how voting patterns in state elections have also nationalized in recent decades.
There is an active debate about how much of the growing geographic concentration of each party’s coalitions is due to residential sorting (Bonica et al. 2017; Mummolo and Nall 2017), cohort effects (Ghitza and Gelman 2014), racial polarization and geographic changes in the distribution of minority populations (Bowler and Segura 2011), or individuals’ switching parties (e.g., Levendusky 2009a; Highton and Kam 2011).
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Acknowledgements
We are grateful for helpful conversations with Chris Tausanovitch and for feedback from Howard Rosenthal and participants at the 2016 ASU Goldwater Conference on Campaigns, Elections and Representation and the 2016 Midwest Political Science Association and American Political Science Association conferences. We appreciate the research assistance of Melissa Meek, Rob Pressel, Stephen Brown, Alex Copulsky, Kelly Alexander, Aneesh Anand, Tiffany Chung, Emma Frank, Joseff Kolman, Mathew Peterson, Charlotte Swasey, Lauren Ullmann, Amy Wickett, Julie Kim, Julia Han, Olivia H. Zhao, Mustafa Ben, Szabolcs Kiss, and Dylan DiGiacomo-Stumm. Upon publication, the data and code necessary to replicate the analysis in this article will be posted in the Harvard Dataverse.
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Caughey, D., Dunham, J. & Warshaw, C. The ideological nationalization of partisan subconstituencies in the American States. Public Choice 176, 133–151 (2018). https://doi.org/10.1007/s11127-018-0543-3
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DOI: https://doi.org/10.1007/s11127-018-0543-3
Keywords
- Representation
- Public opinion
- Ideology
- Nationalization
- Congress
- State politics
JEL Classification
- D72
- H1
- R50