This page has information about the main categories of presidential and congressional primary elections in the United States (open, closed, semi-closed, and others) and puts each state into one of these categories. You can use this information to help find out if you are eligible to vote in presidential and congressional primaries in your state.

Much of the rules listed here can be changed by an internal political party process. Consequently, sometimes one political party will use one process while another political party uses a different process. This sometimes makes it difficult to track changes. If any of the information below has changed, please email us at [email protected]

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Open Primaries

In an open primary, voters of any affiliation may vote in the primary of any party. They cannot vote in more than one party's primary, although that prohibition can be difficult to enforce in the event a party has a primary runoff election. In many open primary states, voters do not indicate partisan affiliation when they register to vote.

One area of contention in open primaries is "crossover" voting. It most often involves voters affiliated with one political party voting in the primary of another political party to influence that party's nomination. For example, if a district routinely elects the Democratic nominee, Republican voters may vote in the Democratic party primary to attempt to influence the outcome. This could be a good-faith attempt to select a more conservative Democratic nominee who would be palatable to the Republican voters, or it could be sabotage, an attempt to nominate a weaker candidate who is easier to defeat in the general election.

Closed Primaries

In a closed primary, only voters registered with a given party can vote in that party's primary. States with closed primaries include party affiliation in voter registration so that the state has an official record of what party each voter is registered as.

Closed primaries preserve a party's freedom of association by better ensuring that only members of the party influence that party's nominees, but critics claim that closed primaries can exacerbate the radicalization that often occurs at the primary stage, when candidates must cater to their party's "base" rather than the political center.

In a few states, independent voters may register with a party on Election Day. However, they must remain registered with that party until they change their affiliation again. A handful of states even allow voters registered with one party to switch their registration at the polls to vote in another party's primary. In these rare instances, a closed primary can more closely resemble open or semi-closed primaries than the closed primaries of other states. 

Semi-Closed Primaries

In a semi-closed primary, unaffiliated voters may choose which party primary to vote in, while voters registered with a party may only vote in that party's primary. Representing a middle ground between the exclusion of independent voters in a closed primary and the free-for-all of open primaries, the semi-closed primary eliminates concerns about voters registered in other parties from "raiding" another party's nominating contest.

People who align with a given party may theoretically still vote in another party's primary if they are registered as independent. The potential for such tactical party registration is also present in the strictest of closed primaries.



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Top Two Primaries

Under "Top Two," political parties do not nominate candidates at all. Instead, all candidates, regardless of party affiliation, run on the same primary ballot. The top two vote-getters then face off in the general election, again regardless of party affiliation. This means that the general election always has exactly two candidates on the ballot, and those two candidates may be from different political parties or from the same political party.

California and Washington use Top Two for state and congressional offices. Nebraska uses a Top Two system but without party labels on the ballot at all for the election of its nonpartisan state legislature.

Learn more here: How Top Two Compared to Ranked Choice Voting

The Louisiana Primary System

The Louisiana system, sometimes called the "Cajun Primary," eliminates the primary election altogether. Instead, all candidates, regardless of party affiliation, run on the same ballot in November. If a candidate receives more than half of the votes, that candidate is elected. If no candidate wins with a majority, the top two vote-getters face off in a December runoff election. Qualified absentee voters receive a ballot for the November election and a ranked ballot for the December runoff, so that they can vote as normal in the general election and then have their ranked ballot count for whichever runoff candidate they ranked highest in the runoff election.

Although Louisiana law refers to the election in November as the "primary" and the December runoff as the "general" election, the November election takes place on the federally mandated Election Day and most candidates win office by receiving a majority vote in that election, so it is best understood as a general election, with the December election as a contingent runoff.

The Louisiana system is sometimes mistakenly equated with the Top Two system, but holding the first election in November and electing any candidate with more than 50% of the vote in that election makes it sufficiently distinct that it should not be understood as a mere variant of Top Two.

Top Four Primaries

Alaska uses a variant on Top Two which allows four candidates to advance to the general election instead of two. This gives voters more choices during the general election when turnout is typically highest, reduces the chance that one major party will be shut out of the general election, and improves the chances for a minor-party or independent candidate to appear in the general election.

In Alaska, the general election is decided by ranked choice voting among the four candidates.


17-Year-Old Primary Voting

FairVote advocates that states and political parties act to allow citizens who will be 18 years old on or before the general election to vote in their party’s corresponding primary or caucus. A notable portion of citizens who have the right to vote in the general election in November currently do not have a voice in determining who will be on that general election ballot. Granting voting rights in primaries and caucuses to these 17-year-olds is only fair and will increase their political engagement through participation. Policymakers can implement this reform by state law or party rule.

The Facts: 17-Year-Old Primary Voting

17-year-olds can vote in Congressional and/or Presidential primaries and caucuses in a large number of states, including Alaska, Connecticut, Delaware, Hawaii, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland, Mississippi, Nebraska, Nevada, North Carolina, Ohio, South Carolina, Virginia, Vermont, Washington, West Virginia, and Wyoming. Seventeen-year-olds may also vote in District of Columbia primaries.

  • In Alaska, Hawaii, Washington, and Wyoming 17-year-old Democrats may caucus, but not 17-year-old Republicans. 
  • This patchwork policy creates confusion and can potentially disenfranchise eligible voters. Parties should act nationally to make this practice a norm.

Voting when young forms a lifetime habit:

  • Parties have a self-interest in encouraging this policy—if a 17-year-old votes in a particular party’s contest, that young person may vote for that party for decades.
  • Studies show youth will vote if asked to do so—this policy increases youth engagement in the political process by creating an ethos of participation from a younger age. Once a person votes, that person is likely to vote again.


How Parties Can Enact 17-Year-Old Voting

17-year-old primary and caucus voting does not require state legislative action. Many states adopting this policy have done so by state law, but others have by changing state party rules. 

  • State parties have broad authority over their nominating contests.
  • They may request to allow 17-year-old primary voting by asserting their First Amendment freedom of association rights.

Primary voting rights for 17-year-olds is legal and does not change the voting age.

  • Only those 17-year-olds who will be 18 by the general election may vote in the corresponding primary election or caucus. FairVote's proposal treats the nomination contest as an integral part of the general election in which these citizens can vote.
  • The 26th Amendment prevents states from denying suffrage to 18-year-olds, but does not prevent states from establishing 17-year-old primary and caucus voting.


State-by-State Facts: 17-Year-Old Voting in Primary Elections




  • Sample letter of support for 17-year-old primary voting legislation in California from Fairvote
  • FairVote case study on the Constitutionality of 17-year-old primary voting in Maryland
  • Policy brief on a proposed bill in the New Mexico legislature to adopt 17-year-old primary voting.

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