Open vs closed primaries

Open vs closed primaries, explained.

Last updated: November 2026

In a closed primary only registered party members can vote; in an open primary any registered voter can.

There are five kinds of primary, from closed, where voters without a party get no ballot, to nonpartisan, where every voter receives one ballot listing every candidate. 15 states use closed primaries. Nonpartisan open primaries treat every taxpaying voter equally.

Which is better, open or closed primaries?

For voters who are not in a party, open primaries are better, because closed primaries give them no vote in the round that often decides the race. Closed primaries mainly serve parties that want members alone to pick nominees. A closed system can still suit a voter who is a committed party member and wants nominees chosen only by fellow members.

Closed primaries vs open primaries: side by side

Primary types compared from our audit
Type	Who can vote	What an independent gets	How many	Example
Closed	Registered party members only	No ballot	15 states	New York, Maryland
Semi-closed	Party members, plus unaffiliated voters who pick one party	One party ballot	10 incl. D.C.	Rhode Island
Semi-open	Any voter may request a party ballot; choice may be recorded	One party ballot	3 states	Colorado
Open	Any voter picks a party ballot on election day	One party ballot	Varies by count	Alabama
Nonpartisan (Top-Two, top-four)	Every voter, one ballot, all candidates	Full ballot, every candidate	California, Washington, Alaska (state races)	California

Each primary type in plain terms

Closed primary

Only voters enrolled in a party may vote in that party's primary. New York is the clearest example: its voters must declare a party affiliation by February 14 on a public record to vote in a June primary. The rule is being challenged in federal court in Rieckhoff v. Berger.

Semi-closed primary

Party members vote in their own primary and unaffiliated voters may choose one party, sometimes by affiliating at the polls. In Rhode Island, where 51.9% of voters are independent, this is the rule. It is an improvement that still ties voting to party labels.

Semi-open and open primaries

Any voter can request a party ballot. In a semi-open state like Colorado, that choice may be recorded. In an open state like Alabama, voters do not register by party at all and simply pick a ballot. Either way, the voter still sees only one party's candidates.

Nonpartisan open primary

All candidates appear on one ballot, every voter takes part, and the top finishers advance regardless of party. California adopted the Top-Two through Proposition 14, passed in 2010. Alaska uses a top-four version for state races.

How to find out which primary your state uses

Check your registration status and party on your state election office website.
Look up your state on the state voter data pages, which list the primary type and rules.
Note any deadline to change party, which can fall months before the primary.
Check whether presidential primaries follow different rules from state races, as they do in Alaska.

The state-by-state list of open primaries collects the classifications in one place, and the open primaries overview explains the nonpartisan model.

Support open primaries

Common questions

What is the difference between open and closed primaries?: In a closed primary, only voters registered with a party can vote in that party's primary. In an open primary, voters can participate without joining a party. Between the two sit semi-closed and semi-open systems, and at the most open end are nonpartisan primaries, where every candidate and every voter share one ballot.
What is a semi-closed primary?: In a semi-closed primary, registered party members vote in their own party's primary, while unaffiliated voters may choose one party's ballot. Voters registered with a different party cannot cross over. IVP describes this as an improvement over closed primaries that still ties participation to party labels. Rhode Island is one semi-closed state.
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. Colorado is a semi-open state. It is more open than a closed system, but the voter still takes part by choosing a party ballot rather than voting on one shared ballot.
Which is better, open or closed primaries?: The Independent Voter Project holds that open, nonpartisan primaries are better for voters because they give every taxpayer an equal vote in a publicly funded election. Closed primaries suit people who want party members alone to pick nominees. For the 63 million voters registered as independent or unaffiliated, only open systems guarantee a voice in the deciding round.
Do open primaries let the other party sabotage a primary?: That concern, often called party raiding, is one of the most common arguments for closed primaries. Nonpartisan top-two systems are designed to sidestep it, because there are no separate party primaries to raid. Every voter receives the same ballot listing every candidate, and the top finishers advance regardless of party.
What is a nonpartisan or top-two primary?: A top-two primary puts every candidate, regardless of party, on a single ballot that every registered voter receives. The two candidates with the most votes advance to the general election, even if they share a party. California adopted this system through Proposition 14 in 2010, a measure authored by the Independent Voter Project.

Read all 43 questions in the open primaries FAQ

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