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New report shows that Top Two nonpartisan primaries are improving California politics

Data shows that Top Two nonpartisan primaries have positively impacted California politics

Unite America
June 8, 2023

The topline: A new report from the Unite America Institute on top-two nonpartisan primaries in California finds that the reform has had positive impacts on electoral politics and governance. While the vast majority of states have experienced a decline in electoral competition and a rise in polarization in recent years, California has trended in a much better direction since reforming its primaries. Analyzing the state across several criteria, the report presents evidence that Top Two in California has decreased polarization, improved voter participation, and increased electoral competition.

In 2010, a bipartisan coalition of reformers — including then Governor Arnold Schwarzenegger and pro-voter business and labor groups — championed Proposition 14, a California ballot initiative to adopt the top-two nonpartisan primary system used in Washington State. Proposition 14 passed with 54% support from voters and was implemented in 2012. Years of data since implementation now provide important insights on the reform’s impact.

In a new report from the Unite America Institute, Unite America Democracy Fellow Dr. Richard Barton finds that top-two nonpartisan primaries in California have had positive impacts on electoral politics and governance. The report tests several hypotheses that relate to polarization, voter participation, electoral competition, and party power (to name a few). It also aggregates existing academic research on nonpartisan primaries, contributes original analysis, and identifies opportunities for future research. 

In a top-two nonpartisan primary, all candidates run on the same ballot with their partisan affiliation (if applicable) listed on the ballot, and all voters are eligible to participate. The top two finishers in the primary advance to the general election, which is guaranteed to have a majority winner with just two candidates on the ballot. Top Two is meant to enfranchise all voters in every election, increase electoral competition, and help produce more representative elected officials. 

A summary of the report’s main findings are included below. 


According to the most widely-respected political science measure of state legislator ideology, from 2013 through 2018, western states’ legislatures polarized more than those in any other region of the country. California, however, is an exception. It is one of only five states that depolarized during that time frame. 

Additional research gives us reason to believe that the top-two system is contributing to depolarization at the federal level as well: A study from scholar Christian Grose found that newly-elected members of Congress from states with nonpartisan primaries — California, Washington, and Louisiana — are up to 18 percentage points less extreme than new members from states with partisan primaries. Further, this report replicates and extends Grose’s analysis with additional election cycles of data and reaches the same conclusion: Nonpartisan primaries have a statistically significant moderating effect.

Same-party general elections are a major driver of the decreasing polarization seen under Top Two. For example, in a safe Democratic district, top-two primaries can sometimes lead to two Democrats advancing to the general election. In this scenario, the Democratic candidates are incentivized to appeal to all general election voters. Research from Jesse Crosson that analyzed candidates from top-two states found that those who win office in a same-party general election are significantly more moderate than those who defeat a competitor from the other party.

“[Top Two] requires members of Congress to reach out to independents, to Republicans and Democrats, even in the primary and also in the general election. And you just don't see that in the closed primaries as much. The data show that members of Congress running for office in closed primaries are just much more likely to be responsive only to their party’s voters.” — Christian Grose, Political Science Professor at the University of Southern California & Academic Director of the USC Schwarzenegger Institute for State and Global Policy.

Turnout and Meaningful Election Participation

Top-two nonpartisan primaries in California have led to increased primary election participation, and the state is now typically near the top of the nation in primary turnout. In 2020, California had the third-highest primary turnout at 33.3%, while Washington State — another top-two state — had the highest turnout at 42.8%. Further, the most thorough study on the impact of Top Two on voter participation concluded that the reform alone can lead to a turnout increase of up to six percentage points

Top Two also leads to more voters casting meaningful ballots. While all voter participation in any election is important and should be encouraged, it is an unfortunate truth that not all votes matter equally. For example, voters from the non-dominant party in safe seats generally don’t have a say in election outcomes, and participation is less meaningful in these districts compared to competitive elections. A large number of voters fall into this category: According to FairVote, about 62 million eligible voters live in districts that are safe for the political party they oppose. If however, the top-two system is used and two candidates from a safe district’s dominant party advance to the general election, then all general election voters are able to cast meaningful votes. As a result, the report finds that, in 2020, California and the other three states that held nonpartisan primaries for state legislative offices — Washington, Nebraska, and Louisiana — had the four-highest shares of meaningful votes cast in the nation.

 Former Lt. Governor Abel Maldonado (R) on the Democrat vs. Democrat 2016 U.S. Senate Election in CA: “I look at the race as a Republican and say to myself, ‘How nice that you get to vote for a candidate that has a chance of winning in California,’ versus the olden days where you were a Republican voting for a Republican that could never win.”


Top Two increases electoral competition both between and within political parties. When elections are more competitive, voters have more viable choices and elected officials are held accountable. In the two election cycles prior to the implementation of Top Two (2008 and 2010), well over 80% of General Assembly partisan primary elections were uncontested. However, in every election cycle since the reform, fewer than 20% of such primaries are uncontested. 

Congressional general elections have also become more competitive. One simple measure of electoral competitiveness is the vote margin between the winning candidate and their closest competitor. California congressional elections held under Top Two have seen average winning margins that are ten percentage points lower than congressional elections held in the decade prior to reform. Nationally, the average winning margin in congressional elections has only dropped by three percentage points during this same period. 

Further, the report argues that Top Two does not entirely eliminate the role or influence of political parties from the electoral process, which is a common criticism of nonpartisan primaries. For instance, party organizations still endorse candidates in general elections, including when the matchup features two candidates from their party. When a party endorses in a same-party general election, the party-endorsed candidate wins about 70% of the time, demonstrating the reform does not negate party influence in electing their preferred candidate.

“[Top Two] gives a lot more opportunity to take on someone in your own party. It allows for new voices to emerge…look at the amount of new people that have come into Congress, to the state house, to the state Senate because of the new system.” — Rep. Ro Khanna (D)


Top Two is not a panacea for the problems plaguing our politics, but evidence suggests the reform produces much better results than the status quo partisan primary. Top Two is also not the only reform gaining traction: Alaska’s novel use of a top-four nonpartisan primary saw similarly hopeful outcomes, especially when it came to competition and giving voters meaningful choice in their representation.

Nevertheless, there is much to learn about nonpartisan primaries, and the impacts of eliminating partisan primaries in general. For instance, the report suggests that future research should consider Top Two’s impact on descriptive representation. Do reforms that eliminate partisan primaries increase or decrease the representation of traditionally underrepresented groups? There is also much more to learn about how voters make decisions under Top Two, especially in same-party general elections when they cannot rely on mere partisanship as a heuristic. Evidence suggests that less extreme candidates are more successful under Top Two, but it is not clear why.

For now, however, it is evident that Top Two in California has increased voter participation and electoral competition, while decreasing polarization. That is a recipe for a more representative and functional government.