Partisan polarization is perhaps the most broadly consequential development of the last half-century of American politics. The parties have steadily diverged since the late 1960s, and by some measures are farther apart than at any point in American history. The divide is now so great that it is no longer rare for close observers to wonder if the political system can survive without a larger ballast of representatives in the political center. With political elites divided into zero-sum teams, many of the norms of the US democratic system have begun to fray.
A series of reforms have been proposed to reintroduce this center to American politics. The reforms generally share the assumption that the polarization of American elites is not what the mass public wants—that there are institutions standing between the voters and their desired government that steer outcomes toward the poles. One of the most interesting and closely-watched of these reforms has been the so-called Top Two primary system (hereafter, “Top Two”), a radically open and unconstrained version of the uniquely American institution of popular primaries. A traditional closed primary election only allows voters registered with a party to participate in its nomination contests; an open primary relaxes this constraint to allow participation by at least a subset of non-party members. The Top Two takes this logic near its furthest extreme, offering the same ballot to all voters regardless of party and letting them choose any candidate they like for each office. The two candidates receiving the most votes—also regardless of party—then advance to the general election, raising the novel prospect of intra-party contests in the fall. It turns the primary from its current form—an opportunity for parties to choose their standard-bearers—into a first-stage general election.
In recent years, California and Washington have adopted the Top Two system, raising the reform’s profile and encouraging other states to consider similar changes to their systems. These are forceful experiments testing the role of electoral institutions in modern partisan representation. Moreover, California has also recently tested another radical reform—independent redistricting—with a similar intended effect. If institutional reform is a potential lever in the American democratic system, these reforms amount to grabbing the lever and pulling as hard as possible.
We use the policy changes in these two states for analytical leverage to explore the effect of the political institutions on legislator behavior. Does the system elect more moderate legislators to public office? Might it be a useful tool for counteracting the trend toward greater partisan polarization? Footnote1 To what extent can we even say that partisan polarization is the product of institutions?
Our examination suggests that the Top Two has had a modest and somewhat inconsistent effect on representation since it was adopted in these two states. The evidence of post-reform moderation is stronger in California than in Washington (and even then only for Democrats), but this moderation is partly due to a contemporaneous policy change—radically new district lines drawn by an independent redistricting commission—rather than from the Top Two itself. There are also some signs that a change in term limits might have played a role. However, the Top Two might have helped to arrest growing liberalism among California Democrats, even as many other states have elected Democrats that are increasingly liberal. While it is still early in the policy experiment, at this point the Top Two appears to be of mixed success as a tool for mitigating polarization. At the same time, there might be a somewhat stronger case for redistricting reform than previously understood.
Of the possible institutions, perhaps none has been blamed more often than America’s unusual system of popular primaries. Footnote4 The United States is virtually alone in the world in leaving most decisions about party nominees to rank-and-file party members. Proponents of this explanation point to the dismal turnout rates in primary elections and emphasize that primary voters are far more partisan and ideologically extreme than the ones who vote in general elections. When these voters are favored by primary election rules, they end up choosing like-minded candidates to represent the parties. This leaves more moderate general election voters with a suboptimal choice between two extreme partisans, when they might have preferred a choice between more centrist candidates.
If primaries are an important cause of polarization, the most commonly proposed reform has been to open primaries to participation by voters outside the party faithful. With open primaries, the median of the primary electorate moves closer to the median of the general electorate, making it less likely that the preferences of each party’s base voters will determine the final outcome. But open primaries can come in many types, and it is not clear that we should expect all types to be equally effective at promoting the goal of greater moderation in public office. In fact, most open primaries either place limits on which voters can cross party lines in the primary, force voters to choose one party’s primary and vote only for candidates of that party for every office, or both. It is easy to imagine that these designs would significantly discourage crossover voting, and so mitigate any moderating effect.