What is the difference between an open and a closed primary?
In a closed primary, only registered party members may vote. In an open primary, any registered voter - including independents - may participate. Semi-open and semi-closed variations also exist.
The terms open and closed describe who is eligible to participate in a party's primary election. In a closed primary, only voters who are registered members of that party may vote. A registered Democrat cannot vote in the Republican primary, and vice versa.
An open primary allows any registered voter to participate in either party's primary, regardless of their own registration. A registered Republican could choose to vote in the Democratic primary (or the other way around), though they can only vote in one party's primary.
Semi-open primaries allow registered independents (unaffiliated voters) to choose which party's primary to participate in, while registered party members must vote in their own party's primary. Semi-closed systems give parties the option to allow or exclude independents.
The rules vary by state and party. For 2028, the exact format for each state's primary will depend on existing state law and any new party rules. Open primaries tend to produce more moderate nominees because they allow participation from the ideological center; closed primaries tend to favor candidates whose appeal is strongest with the party's base.
Related questions
Can I change my registration to vote in a different party's primary?
Does the type of primary affect delegate allocation?
Related explainers
Primary voters choose delegates who will represent them at the party's national convention. The candidate who wins enough delegates - typically a majority - becomes the party's nominee.
A primary is a standard secret-ballot election run by the state government. A caucus is a series of local party meetings where participants publicly declare their support and may be persuaded before delegates are allocated.
Voter registration is handled by each state. Visit vote.gov or your state election authority's website to check eligibility, register, or update your registration before the deadline.