With Super Tuesday just days away, the national media remains focused on the presidential horse race, with 15 states and American Samoa deciding on party nominees. But state primaries decide the candidates for the offices that set most of the nation’s public policy, including governors, legislators, secretaries of state and attorneys general, among others.
Most state primaries fall into one of five categories: closed; partially closed; open to unaffiliated voters; partially open; and open. The key distinction between the categories is whether nonparty members may participate in a party’s primary:
- Closed primaries permit only registered party members to participate; closed primary states without partisan voter registration restrict access to “bona fide” members of a party, with criminal penalties for violations.
- Partially closed primaries give parties the option to allow nonparty members to participate if the decision is made prior to each primary election. For example, West Virginia is a partially closed state where Democrats permit unaffiliated voters to participate in their primaries, while Republicans do not.
- Primaries open to unaffiliated voters allow participants not affiliated with any party, major or minor, to participate in parties’ primaries.
- Partially open primaries allow any voter on Election Day to pick any party’s primary ballot, but the voter will automatically be registered as a member of the party whose ballot they choose. For example, if a Democratic or unaffiliated voter selects the Republican primary ballot, they will be re-registered as a Republican and would need to affirmatively change their party registration later to revert to their prior affiliation.
- Open primaries permit all voters to participate in any party’s primary without changing their affiliation.
States rarely amend their primary systems. On average, just one state switches primary types every two to three years, and these changes have tended to make the primary more open—but not always. Three states—Louisiana, Tennessee and Wyoming—have moved in 2023 and 2024 to strengthen the influence party members have over their own primaries. The degree of change varied: Louisiana moved this year from its all-comers primary to an open-to-unaffiliated primary for some offices. Last year, Tennessee added criminal penalties for participating in a party’s primary without being a “bona fide” member of the party, and Wyoming moved to a closed primary system where only party members may participate (and they must affiliate with the party by late winter). In total, 12 states have changed their primary systems since 2000.
More change may be in the air. Both Texas and Mississippi are considering closing their primaries, though the degree to which they may close is not known. On the other side, at least one state, Nevada, will vote on a ballot measure this fall to abolish its closed primaries in favor of a model similar to Alaska’s new “top four” model, wherein all candidates from all parties run on the same primary ballot, and the top four (five, in Nevada) go on to the general election. Measures in other states may also qualify for this fall’s ballot.
To reflect the possibility of a sudden increase in these newer models for selecting party nominees, NCSL has created a new category of primaries outside the open-to-closed scale: the “multiparty” primary. These systems divorce the concept of party nominees from primary elections by placing all candidates on a single ballot regardless of party, allowing multiple candidates from the same party to advance to the general election. On the flip side, a major party could be excluded from the general election altogether. In addition to Alaska’s top-four model, the multiparty category includes the similar “top-two” systems used in California and Washington since 2010 and 2006, respectively. It also includes Nebraska’s primaries for legislative office, where the top two candidates in a single nonpartisan primary advance to the general election. Five states currently use a multiparty primary.
Ben Williams is the associate director of NCSL’s Elections and Redistricting Program.
Adam Kuckuk is a policy analyst in NCSL’s Elections and Redistricting Program.
NCSL is your home for news on state primaries. As we move through the spring and summer, keep up with the latest coverage on NCSL’s X, Instagram and LinkedIn accounts. For more information on state primaries, visit NCSL’s State Primaries toolkit.