Walter and Wilson hold up California’s top-two primary as a possible. This has been investigated as well. Doug Ahler, Jack Citrin, and Gabriel Lenz conducted an experiment where people voted either using the new top-two ballot or the old closed primary ballot. Moderate candidates fared no better when people voted with the top-two ballot. Thad Kousser, Justin Phillips, and Boris Shor investigated the effect of the top-two primary on representation. They found that legislators tended to stray further from their district’s average voter under the top-two primary than before. In other words, the new California system has improved neither polarization or accountability.
Why don’t these reforms appear to work? There are a variety of reasons. Perhaps there aren’t enough true independents voting to make open primaries a means of reducing polarization. Voters may lack the necessary information or aptitude to distinguish among more moderate and more extreme candidates. Or party elites and donors may ensure that only extreme candidates end up deciding to run.
Walter also cites low turnout in primary elections as a factor. Would increasing turnout in primary elections make them less likely to induce dysfunction or polarization? I’m doubtful. The political science research on primary voters shows — in contrast to conventional wisdom — that they are not much more, or even any more, ideologically extreme than partisans who don’t vote in primaries. Lynn Vavreck and I analyzed a large survey from 2008 that matched respondents to actual voter file records, so that we can compare real primary voters and non-voters (rather than relying on inaccurate self-reported turnout in the survey). Here is how Democrats and Republicans who voted in the primary and general elections compare to those who voted only in the general election.
Those who voted in the primary were clearly more interested in politics but did not have very different views on issues (with the possible exception, for Republicans, of raising taxes on the wealthy). Other research finds a similar pattern; see here or here or here. Given these findings, increasing primary turnout would not necessarily create a very different electorate and therefore different incentives for candidates or incumbents.
To be sure, there are caveats. For one, California’s system is new, and perhaps things will change as parties and candidates adapt to the system. Moreover, none of the authors cited herein would rule out the possibility that changes in primary rules might reduce polarization.
But as of now, the available research suggests that changing primary elections probably won’t create less polarization and more civility — in state capitols or on Capitol Hill.