Explainer · Primary types
Open vs closed primary: definition, pros and cons
Last updated: November 13, 2026
An open primary lets any registered voter take part, while a closed primary limits each party's ballot to that party's enrolled members.
The Primary Desk defines an open primary as a taxpayer-funded primary election that does not require party membership to vote. That single rule decides whether independent and unaffiliated voters have a say in the round that, in most districts, settles who wins.
What is the difference between an open and closed primary?
The difference is who gets a ballot. In a closed primary, such as New York's, a voter must be enrolled in a party, often months ahead, to vote in its primary. In an open primary, any registered voter can participate on primary day. Nonpartisan versions like California's top-two go further, putting every candidate on one ballot for every voter.
Quotable definition
Open primary definition
There are two families of open primary. In a partisan open primary, each party still holds its own contest, but voters choose which party's ballot to use without registering with that party. Alabama is an open primary state. In a nonpartisan open primary, there is one ballot listing every candidate, and the top finishers, two in California and Washington or four in Alaska, advance to November.
A closed primary is the opposite: only enrolled party members get that party's ballot. There are 15 closed states. Semi-closed primaries, used in 10 jurisdictions, let unaffiliated voters pick one party's ballot while blocking members of other parties. Semi-open primaries, in 3 states, let any voter request a ballot but may record the choice.
Every primary type compared
| System | Who can vote | Unaffiliated voters? | Example states | Count |
|---|---|---|---|---|
| Closed | Only voters enrolled in the party | No | New York, Pennsylvania, Florida | 15 |
| Semi-closed | Party members, plus unaffiliated voters | Yes, they pick one party ballot | Rhode Island, Massachusetts, North Carolina | 10 |
| Semi-open | Any voter, but the ballot choice may be recorded | Yes | Arizona, Colorado | 3 |
| Open | Any voter chooses a party ballot | Yes | Alabama | See state guide |
| Top-two (nonpartisan) | All voters, one ballot, top two advance | Yes | California, Washington | 2 statewide |
| Top-four with ranked choice | All voters, one ballot, top four advance | Yes | Alaska | 1 |
What are the pros and cons of open primaries?
Pros of open primaries
- Every taxpayer can vote in an election paid for with public money.
- Independents get a voice in the round that often decides the seat. Over 80% of elections are no longer competitive in the general election.
- Candidates have a reason to appeal beyond their party base.
- Voters are not forced to put a party affiliation on a public record just to get a ballot.
Cons of open primaries
- Parties have less control over who carries their label.
- Some voters cross over. Crossover voting is 3 to 20 percent.
- In top-two systems, vote splitting can send two candidates from the same party to November.
- Minor-party candidates may rarely reach the general election in single-ballot systems.
Why do parties prefer closed primaries to open primaries?
Parties prefer closed primaries because they keep nominee selection in members' hands. A closed primary protects a party's freedom of association, the same constitutional principle the plaintiffs in New York's Rieckhoff v. Berger case acknowledge. It limits outside influence over who carries the party label and rewards the loyal base voters who reliably turn out.
Reform advocates answer that closed primaries are publicly funded and administered, yet they shut out voters who decline to join. This insulates parties from competition, and the New York case contends that a voter's right not to join deserves the same protection as a party's right to exclude.
Does crossover voting undermine open primaries?
It is the most common objection, and the numbers keep it in proportion. Crossover voting in open primaries typically runs 3 to 20 percent, and most crossover voters are choosing a candidate they prefer, not sabotaging the other side. Nonpartisan systems like top-two avoid the issue entirely, because there is no other party's primary to cross into.
Open vs closed primary questions
See all 47 questions in the FAQWhat is the difference between an open and a closed primary?
The difference is who gets a ballot. In a closed primary, only voters enrolled in a party can vote in that party’s primary, so unaffiliated voters sit out. In an open primary, any registered voter can participate. Semi-closed and semi-open systems fall in between, letting unaffiliated voters choose a party ballot under set rules.
What is an open primary?
An open primary is a primary election in which any registered voter can take part without first joining a political party. In a traditional open primary the voter picks one party's ballot on election day. In a nonpartisan open primary, such as California's top-two, every candidate appears on one ballot and the top finishers advance to November.
What are the pros and cons of open primaries?
Supporters say open primaries let every taxpayer vote in elections they fund, reward candidates who appeal beyond their base, and give independents a voice in the round that often decides the race. Critics say they weaken a party’s ability to choose its own nominee, invite crossover voting, and can produce same-party general elections.
Why do parties prefer closed primaries to open primaries?
Parties prefer closed primaries because they keep nominee selection in the hands of members. Closed rules protect a party's freedom of association, limit outside influence over who carries its label, and reward loyal base voters. Reform advocates respond that the same rules insulate parties from competition while all taxpayers pay for the election.
Do open primaries lead to crossover voting or raiding?
Some crossover happens, but it is limited. The Primary Election Types explainer states that crossover voting in open primaries typically runs 3 to 20 percent. Organized raiding, where one party’s voters try to nominate the other party’s weakest candidate, is a common worry, but crossover voters more often simply prefer a candidate in the other contest.
What is a semi-closed primary?
A semi-closed primary lets registered party members vote in their own party's primary and lets unaffiliated voters choose one party's primary, but blocks members of other parties from crossing over. Rhode Island works this way. The Independent Voter Project's state guide counts 10 semi-closed jurisdictions, including Massachusetts, New Hampshire, North Carolina, and Utah.
What is a semi-open primary?
In a semi-open primary any voter can request a party's ballot, but that choice may be recorded and treated as a public record of which primary you chose. The Independent Voter Project's primary guide counts three semi-open states, including Arizona and Colorado. Check your state election office for exactly how your ballot choice is recorded.
Your next step
Support open primaries first. Then explore More Choice Voting.
Opening the primary is the reform every other change builds on. Add your name, then read how More Choice Voting takes the next step.