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Open Primary Guide is a plain-English guide that explains what open primaries are and which states have them, so any voter can find their rules in a minute.
Primary rules are written state by state, and the differences are easy to miss. A voter can be welcome in any primary in Ohio, limited to one party ballot in North Carolina, and shut out entirely in New York. Because 87% of 2024 congressional races were effectively decided in primaries, those rules decide whose voice counts.
This guide puts the definitions, the 2026 state list, and the key numbers in one place, written for voters, students, and anyone who has asked "can I vote in my state's primary?"
The Independent Voter Project is a national, nonpartisan election-reform organization founded in 2006. It authored California's Proposition 14, the 2010 top-two primary, and works for open primaries for every voter, More Choice Voting, and limits on super PACs through legal action, policy research, and grassroots organizing.
If you want primaries open to every voter, the first step is supporting open primaries. After that, explore More Choice Voting, which pairs an open primary with ranked choice or approval voting in the general election.
Every number names its source, and every state classification follows one consistent framework. Read the methodology for details, and always confirm deadlines with your state election office.
The first step is supporting open primaries for every voter. Next, see how More Choice Voting builds on them.
Open primaries are primary elections where any registered voter can choose one party ballot without first joining that party. You decide which primary to vote in on election day or when you request a mail ballot. In 2026, 20 states use fully open primaries.
The Independent Voter Project, a nonpartisan 501(c)(4) founded in 2006, leads a national effort for open primaries for every voter. It wrote California's Proposition 14, defended it in court, and in October 2026 filed Rieckhoff v. Berger challenging New York's closed primaries in federal court.
The simplest first step is to add your name to an open primaries petition, which takes about 30 seconds. The Independent Voter Project runs a national open primaries petition and lists ways to sign, donate, or subscribe on its take-action page. After that, explore More Choice Voting, which builds on open primaries.
More Choice Voting pairs an open, single-ballot primary with ranked choice or approval voting in the general election. All candidates appear on one primary ballot, the top finishers advance, and voters then rank them. Alaska's top-four system, adopted in 2020, is a working example of this approach.
Proposition 14 was the 2010 ballot measure that replaced California's party primaries with a nonpartisan top-two primary. It was authored by the Independent Voter Project and passed by voters. Today nearly 40 million Californians live under a primary system that does not require party membership to vote.
