Research on All-Party Primaries

Sinclair, O’Grady, Miller & Murphy, “Participation and Competition in Top-Two Elections: Trade-Offs in Election Reform.” State Politics & Policy Quarterly. 2026. | Finds that Top Two increases meaningful competition in safe districts and shifts decisive elections from low-turnout partisan primaries to higher-turnout general elections, increasing meaningful voter participation. Winners must secure support from substantially larger portions of the electorate, strengthening accountability without favoring any particular ideological faction. Notably, in Top Two general elections in safe districts, incumbents must compete before larger electorates, and even poorly resourced candidates can generate strong challenges — demonstrating that dominant-party districts are not structurally insulated from insurgent campaigns.

Donovan, Micatka & Tolbert, “Can nonpartisan primaries boost turnout and lessen demographic disparities?” PLOS One. 2025. | Finds that nonpartisan primary systems are associated with higher turnout in congressional primaries and reduced demographic disparities in participation, suggesting that primary reform can broaden engagement and make primary electorates more representative.

Micatka, Tolbert & Boatright, “All Candidate Primaries, Open Primaries, and Voter Turnout.” Journal of Political Institutions and Political Economy. 2024 | Finds that voters in Top Two primary states are more likely to vote in congressional primaries than those in partisan primary systems. Partisans and especially independents both participate at higher rates.

Kamarck and Podkul, “The 2018 Primaries Project: The demographics of primary voters.” The Brookings Institution. 2018. | Finds that partisan primary electorates are both more extreme and less diverse on multiple dimensions, including race, than general election electorates.

Ferrer et al, “The Effect of Open Primaries on Turnout and Representation.” Bipartisan Policy Center. 2024. | Finds that partisan primary voters are less representative and diverse than general election electorates; on the other hand open primaries tend to be associated with higher and more diverse turnout.

Macomber, “Nonpartisan Primaries Increase Primary Turnout.” Unite America Institute. 2024. | Finds that primary turnout increases under nonpartisan primaries.

Hall, “State elections, policy choices, and accountability.” Institute for Economic Policy Research, Stanford. 2021. | Finds that legislators operating in more competitive electoral environments are more responsive to voter concerns and display more accountability.

Barton, “California’s Top-Two Primary: The Effects on Electoral Politics and Governance.” Unite America Institute. 2023 | Finds that CA’s transition to Top Two elections was associated with higher voter turnout in elections and less partisan behavior among elected officials.