Can nonpartisan primaries boost turnout and lessen demographic disparities?

U.S. congressional general elections are largely uncompetitive, featuring candidates who emerge from low-turnout primaries. Voters in these primaries are unrepresentative of the broader electorate; primary voters tend to be older and wealthier. Previous research has focused on how open and nonpartisan primaries may affect the turnout of unaffiliated voters in primaries. We are interested in the downstream effects of opening primaries, including their estimated effects on turnout of younger voters and those with lower socioeconomic status. This study uses large samples of administrative voter file data to investigate whether nonpartisan and open primaries were associated with higher turnout across multiple elections (2018 and 2022). Results find open primaries were not associated with higher individual-level turnout. We found that nonpartisan primaries were associated with higher turnout across all age groups, including both low- and high-income groups, as well as low- and high-education groups. The results find the greatest proportionate increases for younger voters.