Check out the Bipartisan Policy Center's report
In March 2023, Joshua Ferrer and Michael Thorning of the Bipartisan Policy Center authored the organization’s latest edition of its midterm primary election turnout report. They find that just 21.3% of all eligible voters participated in primary elections during the last cycle. However, they find states with nonpartisan primaries have higher primary turnout than those with partisan primaries. Specifically, their statistical analysis found that a state can increase its primary turnout by three percentage points, on average, by switching to a nonpartisan primary system. The report concludes with several other policy recommendations states could implement in order to boost primary turnout, such as holding a national primary day and combining state and federal primaries. This report is a great resource for any advocates or state leaders interested in encouraging greater voter participation in ever-important primary elections.