American Political Science Review (2018)112.4.826-843 doi:10.1017/S0003055418000515 American Political Science Association 2018 Primaries and Candidate Polarization:Behavioral Theory and Experimental Evidence JONATHAN WOON University of Pittsburgh o primary elections cause candidates to take extreme,polarized positions?Standard equilibrium analysis predicts full convergence to the median voter's position with complete information, but behavioral game theory predicts divergence when players are policy-motivated and have out-of-equilibrium beliefs.Theoretically,I show that primary elections can cause greater extremism or moderation,depending on the beliefs candidates and voters have about their opponents.In a controlled incentivized experiment,I find that candidates diverge substantially and that primaries have little effect on average positions.Voters employ a strategy that weeds out candidates who are either too moderate or too extreme,which enhances ideological purity without increasing divergence.The analysis highlights the importance of behavioral assumptions in understanding the effects of electoral institutions. The partisan primary system,which favors more ideolog- Political scientists have tested this argument,find- ically pure candidates,has contributed to the election of ing that while there is some evidence to suggest more extreme officeholders and increased political polar- that primary elections promote extremism,the em- ization.It has become a menace to governing. pirical record is mixed.Extremists are more likely to Sen.Charles Schumer(D-NY)! win congressional primaries than moderates (Brady. Han,and Pope 2007),and legislators elected under he divergence between candidates and legisla- closed primaries take more extreme positions than tors from the two major parties is an enduring feature of the American political landscape(An- legislators elected under open primaries(Gerber and Morton 1998).But other analyses find that polariza- solabehere,Snyder,and Stewart 2001;Bonica 2013; tion is largely unrelated to the introduction of direct Poole and Rosenthal 1984,1997).and the fact that polarization is at historically high levels is a signifi- primaries (Hirano et al.2010)and to the variation in the openness of primaries across states(McGhee et al. cant concern for scholars and observers of democratic governance,representation,and public policy(Hacker 2014).At best,primaries may cause polarization un- and Pierson 2006;Mann and Ornstein 2013;McCarty, der limited circumstances(Bullock and Clinton 2011), and despite the divergence of candidate positions,gen- Poole,and Rosenthal 2006,2013).Indeed,politicians eral elections nevertheless exert nontrivial pressure on and the popular press often lay much of the blame for candidates to moderate (Hall 2015:Hirano et al.2010) this phenomenon on partisan primary elections,typ- These findings seem puzzling in light of the basic theory ically employing a simple,intuitively appealing argu- of representation at the heart of this literature that the ment:Candidates take extreme positions because they extremity of primary electorates should directly affect must appeal to partisan primary voters,whose prefer- the extremity of party candidates. ences are more extreme than those of voters in the gen- How,then,should we understand the causal relation- eral election ship between primary elections and candidate position- ing?I examine the connection,both theoretically and Jonathan Woon is a Professor,Department of Political Science,De- partment of Economics(secondary),and Pittsburgh Experimenta experimentally,by comparing elections with and with- Economics Laboratory.4437 Wesley W.Posvar Hall,Pittsburgh,PA. out primaries while holding other features of the elec- 15260(woon@pitt.edu). toral environment constant,including preferences and Thanks to Keith Dougherty,Sandy Gordon,Greg Huber,Scott information.The analysis focuses on a particular as- Moser,Charlie Plott,Danielle Thomsen,Alan Wiseman,the editor and anonymous reviewers,participants at the Yale CSAP American pect of primary elections-how the introduction of vot- Politics Conference.seminar participants at Washington University ers in the candidate selection process affects strategic in St.Louis,University of Oxford (Nuffield College CESS).IC3JM competition between parties-while abstracting away (Juan March Institute),and the Pittsburgh Experimental Economics from many other considerations that might also affect Lab for helpful comments and feedback.I am also indebted to Kris polarization.2 Kanthak for vigorous discussions during the early stages of this project.Previous versions of the paper were presented at the 2014 The contribution of this paper is to develop a more Annual Meeting of the American Political Science Association,the nuanced theoretical understanding of the relationship 2016 Public Choice Society Meeting,and the 2016 Midwest Polit- between primaries and polarization than is portrayed ical Science Association Conference.This research was supported in the existing literature.The key theoretical innova- by the National Science Foundation(SES-1154739)and was ap tion is to move beyond preference-based explanations proved by the University of Pittsburgh Institutional Review Board under protocol PRO14060001.Replication material is available on by treating beliefs as a primitive of the model in a the American Political Science Review Dataverse:https://doi.org/10. way that is ruled out by standard equilibrium analysis 7910/DVN/YUNDMQ. Received:June 27 2016;revised:September 11,2017;accepted:July 12,2018.First published online:September 10,2018. 2 Such considerations include candidate valence,turnout,activists. or campaign contributions (Adams and Merrill 2008:Callander Charles E.Schumer,"Adopt the Open Primary,"New York Times, and Wilson 2007:Hirano,Snyder,and Ting 2009;Hummel 2013: July21,2014. Meirowitz 2005:Snyder and Ting 2011). 826American Political Science Review (2018) 112, 4, 826–843 doi:10.1017/S0003055418000515 © American Political Science Association 2018 Primaries and Candidate Polarization: Behavioral Theory and Experimental Evidence JONATHAN WOON University of Pittsburgh Do primary elections cause candidates to take extreme, polarized positions? Standard equilibrium analysis predicts full convergence to the median voter’s position with complete information, but behavioral game theory predicts divergence when players are policy-motivated and have out-of-equilibrium beliefs. Theoretically, I show that primary elections can cause greater extremism or moderation, depending on the beliefs candidates and voters have about their opponents. In a controlled incentivized experiment, I find that candidates diverge substantially and that primaries have little effect on average positions. Voters employ a strategy that weeds out candidates who are either too moderate or too extreme, which enhances ideological purity without increasing divergence. The analysis highlights the importance of behavioral assumptions in understanding the effects of electoral institutions. The partisan primary system, which favors more ideolog￾ically pure candidates, has contributed to the election of more extreme officeholders and increased political polar￾ization. It has become a menace to governing. — Sen. Charles Schumer (D-NY)1 The divergence between candidates and legisla￾tors from the two major parties is an enduring feature of the American political landscape (An￾solabehere, Snyder, and Stewart 2001; Bonica 2013; Poole and Rosenthal 1984, 1997), and the fact that polarization is at historically high levels is a signifi￾cant concern for scholars and observers of democratic governance, representation, and public policy (Hacker and Pierson 2006; Mann and Ornstein 2013; McCarty, Poole, and Rosenthal 2006, 2013). Indeed, politicians and the popular press often lay much of the blame for this phenomenon on partisan primary elections, typ￾ically employing a simple, intuitively appealing argu￾ment: Candidates take extreme positions because they must appeal to partisan primary voters, whose prefer￾ences are more extreme than those of voters in the gen￾eral election. Jonathan Woon is a Professor, Department of Political Science, De￾partment of Economics (secondary), and Pittsburgh Experimental Economics Laboratory, 4437 Wesley W. Posvar Hall, Pittsburgh, PA, 15260 (woon@pitt.edu). Thanks to Keith Dougherty, Sandy Gordon, Greg Huber, Scott Moser, Charlie Plott, Danielle Thomsen, Alan Wiseman, the editor and anonymous reviewers, participants at the Yale CSAP American Politics Conference, seminar participants at Washington University in St. Louis, University of Oxford (Nuffield College CESS), IC3JM (Juan March Institute), and the Pittsburgh Experimental Economics Lab for helpful comments and feedback. I am also indebted to Kris Kanthak for vigorous discussions during the early stages of this project. Previous versions of the paper were presented at the 2014 Annual Meeting of the American Political Science Association, the 2016 Public Choice Society Meeting, and the 2016 Midwest Polit￾ical Science Association Conference. This research was supported by the National Science Foundation (SES-1154739) and was ap￾proved by the University of Pittsburgh Institutional Review Board under protocol PRO14060001. Replication material is available on the American Political Science Review Dataverse: https://doi.org/10. 7910/DVN/YUNDMQ. Received: June 27, 2016; revised: September 11, 2017; accepted: July 12, 2018. First published online: September 10, 2018. 1 Charles E. Schumer, “Adopt the Open Primary,” New York Times, July 21, 2014. Political scientists have tested this argument, find￾ing that while there is some evidence to suggest that primary elections promote extremism, the em￾pirical record is mixed. Extremists are more likely to win congressional primaries than moderates (Brady, Han, and Pope 2007), and legislators elected under closed primaries take more extreme positions than legislators elected under open primaries (Gerber and Morton 1998). But other analyses find that polariza￾tion is largely unrelated to the introduction of direct primaries (Hirano et al. 2010) and to the variation in the openness of primaries across states (McGhee et al. 2014). At best, primaries may cause polarization un￾der limited circumstances (Bullock and Clinton 2011), and despite the divergence of candidate positions, gen￾eral elections nevertheless exert nontrivial pressure on candidates to moderate (Hall 2015; Hirano et al. 2010). These findings seem puzzling in light of the basic theory of representation at the heart of this literature that the extremity of primary electorates should directly affect the extremity of party candidates. How, then, should we understand the causal relation￾ship between primary elections and candidate position￾ing? I examine the connection, both theoretically and experimentally, by comparing elections with and with￾out primaries while holding other features of the elec￾toral environment constant, including preferences and information. The analysis focuses on a particular as￾pect of primary elections—how the introduction of vot￾ers in the candidate selection process affects strategic competition between parties—while abstracting away from many other considerations that might also affect polarization.2 The contribution of this paper is to develop a more nuanced theoretical understanding of the relationship between primaries and polarization than is portrayed in the existing literature. The key theoretical innova￾tion is to move beyond preference-based explanations by treating beliefs as a primitive of the model in a way that is ruled out by standard equilibrium analysis 2 Such considerations include candidate valence, turnout, activists, or campaign contributions (Adams and Merrill 2008; Callander and Wilson 2007; Hirano, Snyder, and Ting 2009; Hummel 2013; Meirowitz 2005; Snyder and Ting 2011). 826 Downloaded from https://www.cambridge.org/core. Shanghai JiaoTong University, on 26 Oct 2018 at 03:53:04, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0003055418000515