Primaries and Candidate Polarization in complete information environments.I show that The key finding from the experiment is that pri- primaries can cause polarization or moderation,de- maries appear to cause a kind of ideological purity pending on candidates'beliefs about opposing voters rather than greater extremism.Regardless of whether strategic behavior-even when preferences are held there is a primary election or not,I find that subjects constant.To generate this insight,I rely on ideas from take positions that diverge significantly from the me- behavioral game theory,which retains much of the the dian voter's position.This finding lends support for the oretical apparatus from standard game theory while al- behavioral theory.However,the extent to which pri- lowing for key departures(Camerer 2003).Specifically, maries cause polarization is limited.Greater polariza I allow players to have"incorrect"or"nonequilibrium tion only occurs without feedback such that candidates beliefs about others'actions (Crawford.Costa-Gomes. cannot learn about the behavior of others,and this po- and Iriberri 2013).but assume they are nevertheless larization happens because voters tend to select ex- strategic in the sense that they best respond to what tremists over moderates,even though candidate posi- they think other players do (Camerer.Ho.and Chong tions do not vary with the election format.More pre- 2004;Nagel 1995;Stahl and Wilson 1995).The analysis cisely,the analysis reveals that voters do not support demonstrates that changes in preferences alone are party extremists or party moderates unconditionally. not the only cause of polarization.Instead,beliefs and Instead,they select candidates with intermediate posi- expectations about the strategic behavior of others tions,consistent with their own subjective beliefs about play important roles in conditioning the effect of optimal candidate positions,approximately halfway institutions. between the median voter and their own party's ideal I then turn to the laboratory and conduct a series of point.This behavior generates a greater concentra- experiments to test the effects of primaries on candi- tion of candidate positions around an average that di- date positions and to distinguish between behavioral verges from the median voter.Hence,greater ideolog- assumptions.The chief advantage of the laboratory for ical homogeneity reinforces,rather than exacerbates, theory testing is control(Aldrich and Lupia 2011;Falk polarization 4号元 and Heckman 2009;Morton and Williams 2010),so we can be confident that the observed behavior oc- curs under the conditions specified by the theoretical RELATED LITERATURE model.Importantly,subjects face the same key trade- My analysis follows a long tradition of using spatial off in the experiment as the actors do in the theoretical voting models to understand elections.Although ex- model between increasing the favorability of winning isting spatial models predict candidate divergence in outcomes versus increasing the probability of winning. elections with primaries,they do so in isolation and In the lab,theoretically relevant quantities of interest do not compare them explicitly to elections without that are difficult to measure using observational data primaries (Aronson and Ordeshook 1972;Coleman with any accuracy or without strong assumptions (in 1972:Owen and Grofman 2006).These models also as- particular,preferences and positions)are also known sume that general election outcomes are probabilistic, exactly.Furthermore,experimental manipulations per- which is theoretically consequential because the mech- mit tests of mechanisms not possible using observa- tional data.Thus,laboratory experiments are ideal for anism they rely on to produce divergence is the com- theory testing given their high internal validity.3 bination of policy motivations and uncertainty about which candidate will win the general election-the same forces that generate incentives for candidate di- 3 The main question of interest for theory testing.as Aldrich and Lu- vergence in the absence of primaries (Calvert 1985: pia (2011.90)put it,is"Will people who are in the situations you de- Wittman 1983).Thus,it is unclear from the literature scribe in your model act as you predict?"For related discussions,see whether polarization can be traced to any distinctive Dickson(2011).Palfrey(2006).and especially.Morton and Williams features of primaries per se,as electoral institutions. (2010).While the question of external validity ("To what extent can we generalize from a particular sample?")is an enduring source of By explicitly comparing institutions,my analysis speaks controversy in political science,Falk and Heckman(2009)argue in directly to the connection between primaries and their insightful defense of the value of lab experiments in social sci- polarization. ence that "Behavior in the laboratory is reliable and real:Participants in the lab are real human beings who perceive their behavior as rel- evant,experience real emotions,and take decisions with real eco. nomic consequences"(536).Indeed,there are many precedents for testing theories of elite behavior using laboratory experiments(e.g., strategic than ordinary people (because they have more experi eys Aragones and Palfrey 2007:Frechette,Kagel,and Lehrer 2003:Mor- ence,access to advice,information,etc.),there is surprisingly little ton 1993).Moreover,Druckman and Kam(2011)note that there is evidence to support such claims.To the contrary,recent compar- nothing inherently problematic with using student samples,and there isons by Sheffer et al.(2018)demonstrate that politicians are just as is little evidence to suggest that using undergraduates as stand-ins (and sometimes more)susceptible to choice anomalies than ordinary for elites biases the results in any particular direction (see Morton citizens and Williams 2010,343-7).For example,Potters and van Winden An exception is Jackson,Mathevet,and Mattes (2007),who com- (2000)find significant,but small,differences between students and pare alternative nomination systems in a citizen-candidate frame- lobbyists:Fatas,Neugebauer,and Tamborero(2007)find elites do work.In their model,primary elections affect whose preference is not fit prospect theory as well as students,while studies by Belot decisive in nominating candidates and have no effect if party leaders Duch,and Miller (2015),Cooper et al.(1999),and Mintz,Redd,and and the median party voter have the same preferences.Other formal Vedlitz(2006)suggest that student samples provide a lower bound to models of primary elections largely focus on considerations of voter departures from rational decision-making.Despite the common as. uncertainty,incomplete information,and signaling along with issues sertion that politicians must be better decision makers and more of candidate valence and distributional concerns. 827Primaries and Candidate Polarization in complete information environments. I show that primaries can cause polarization or moderation, de￾pending on candidates’ beliefs about opposing voters’ strategic behavior—even when preferences are held constant. To generate this insight, I rely on ideas from behavioral game theory, which retains much of the the￾oretical apparatus from standard game theory while al￾lowing for key departures (Camerer 2003). Specifically, I allow players to have “incorrect” or “nonequilibrium” beliefs about others’ actions (Crawford, Costa-Gomes, and Iriberri 2013), but assume they are nevertheless strategic in the sense that they best respond to what they think other players do (Camerer, Ho, and Chong 2004; Nagel 1995; Stahl and Wilson 1995). The analysis demonstrates that changes in preferences alone are not the only cause of polarization. Instead, beliefs and expectations about the strategic behavior of others play important roles in conditioning the effect of institutions. I then turn to the laboratory and conduct a series of experiments to test the effects of primaries on candi￾date positions and to distinguish between behavioral assumptions. The chief advantage of the laboratory for theory testing is control (Aldrich and Lupia 2011; Falk and Heckman 2009; Morton and Williams 2010), so we can be confident that the observed behavior oc￾curs under the conditions specified by the theoretical model. Importantly, subjects face the same key trade￾off in the experiment as the actors do in the theoretical model between increasing the favorability of winning outcomes versus increasing the probability of winning. In the lab, theoretically relevant quantities of interest that are difficult to measure using observational data with any accuracy or without strong assumptions (in particular, preferences and positions) are also known exactly. Furthermore, experimental manipulations per￾mit tests of mechanisms not possible using observa￾tional data. Thus, laboratory experiments are ideal for theory testing given their high internal validity.3 3 The main question of interest for theory testing, as Aldrich and Lu￾pia (2011, 90) put it, is “Will people who are in the situations you de￾scribe in your model act as you predict?” For related discussions, see Dickson (2011), Palfrey (2006), and especially, Morton and Williams (2010). While the question of external validity (“To what extent can we generalize from a particular sample?”) is an enduring source of controversy in political science, Falk and Heckman (2009) argue in their insightful defense of the value of lab experiments in social sci￾ence that “Behavior in the laboratory is reliable and real:Participants in the lab are real human beings who perceive their behavior as rel￾evant, experience real emotions, and take decisions with real eco￾nomic consequences” (536). Indeed, there are many precedents for testing theories of elite behavior using laboratory experiments (e.g., Aragones and Palfrey 2007; Frechette, Kagel, and Lehrer 2003; Mor￾ton 1993). Moreover, Druckman and Kam (2011) note that there is nothing inherently problematic with using student samples, and there is little evidence to suggest that using undergraduates as stand-ins for elites biases the results in any particular direction (see Morton and Williams 2010, 343–7). For example, Potters and van Winden (2000) find significant, but small, differences between students and lobbyists; Fatas, Neugebauer, and Tamborero (2007) find elites do not fit prospect theory as well as students, while studies by Belot, Duch, and Miller (2015), Cooper et al. (1999), and Mintz, Redd, and Vedlitz (2006) suggest that student samples provide a lower bound to departures from rational decision-making. Despite the common as￾sertion that politicians must be better decision makers and more The key finding from the experiment is that pri￾maries appear to cause a kind of ideological purity rather than greater extremism. Regardless of whether there is a primary election or not, I find that subjects take positions that diverge significantly from the me￾dian voter’s position. This finding lends support for the behavioral theory. However, the extent to which pri￾maries cause polarization is limited. Greater polariza￾tion only occurs without feedback such that candidates cannot learn about the behavior of others, and this po￾larization happens because voters tend to select ex￾tremists over moderates, even though candidate posi￾tions do not vary with the election format. More pre￾cisely, the analysis reveals that voters do not support party extremists or party moderates unconditionally. Instead, they select candidates with intermediate posi￾tions, consistent with their own subjective beliefs about optimal candidate positions, approximately halfway between the median voter and their own party’s ideal point. This behavior generates a greater concentra￾tion of candidate positions around an average that di￾verges from the median voter. Hence, greater ideolog￾ical homogeneity reinforces, rather than exacerbates, polarization. RELATED LITERATURE My analysis follows a long tradition of using spatial voting models to understand elections. Although ex￾isting spatial models predict candidate divergence in elections with primaries, they do so in isolation and do not compare them explicitly to elections without primaries (Aronson and Ordeshook 1972; Coleman 1972;Owen and Grofman 2006).4 These models also as￾sume that general election outcomes are probabilistic, which is theoretically consequential because the mech￾anism they rely on to produce divergence is the com￾bination of policy motivations and uncertainty about which candidate will win the general election—the same forces that generate incentives for candidate di￾vergence in the absence of primaries (Calvert 1985; Wittman 1983). Thus, it is unclear from the literature whether polarization can be traced to any distinctive features of primaries per se, as electoral institutions. By explicitly comparing institutions,my analysis speaks directly to the connection between primaries and polarization. strategic than ordinary people (because they have more experi￾ence, access to advice, information, etc.), there is surprisingly little evidence to support such claims. To the contrary, recent compar￾isons by Sheffer et al. (2018) demonstrate that politicians are just as (and sometimes more) susceptible to choice anomalies than ordinary citizens. 4 An exception is Jackson, Mathevet, and Mattes (2007), who com￾pare alternative nomination systems in a citizen-candidate frame￾work. In their model, primary elections affect whose preference is decisive in nominating candidates and have no effect if party leaders and the median party voter have the same preferences. Other formal models of primary elections largely focus on considerations of voter uncertainty, incomplete information, and signaling along with issues of candidate valence and distributional concerns. 827 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