June 2023

California’s Top-Two Primary: The Effects on Electoral Politics and Governance

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% voter support and was implemented in 2012. Years of data since implementation now provide important insights on the reform’s impact — and whether or not the reform delivered on advocates’ promises.

Through a synthesis of existing literature, updated data analysis, and new original research, UA’s Democracy Fellow Dr. Richard Barton offers a fresh take on what we know about California’s nonpartisan election reform. Since adopting top-two primaries, the state has: 

  • Depolarized at both the state legislative and congressional level: 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. Additionally, 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; 
  • Introduced more competition in primary elections: 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. Additionally, 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; 
  • Regularly leads the nation in primary turnout, and increased the share of residents who cast a meaningful vote in an election of consequence: 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. 

While top-two nonpartisan primaries are certainly not a panacea for the problems facing our politics — and many unanswered research questions remain — evidence suggests they’re a marked improvement over the status quo partisan primaries. 


Other research