A primary election is an election where political parties choose their candidates for the general election. In a primary election, candidates are nominated rather than elected. In the general election, the nominated candidates from opposing parties face off against one another.
States have specific laws on what defines a political party and the threshold of votes a candidate must receive for nomination. More information on this is available from the National Association of Secretaries of State. Primary elections are administered by state and local election offices on behalf of the political parties. State law determines whether the primary is a partially open, semi-closed, closed, open to unaffiliated voters, open or top-two election.
Primary Election Types by State
Partially Open Primary
The partially open primary system allows voters to cast ballots regardless of party affiliation. Voters do so publicly or it may be construed as an attempt to register with the opposing party. For example, Iowa requires voters to select a party when registering to vote. Still, it permits primary voters to publicly switch parties to cast their ballot on primary election day. This then automatically changes their voter registration to the party whose primary they are participating in.
States with partially open primaries include Illinois, Indiana, Iowa, New Jersey, Ohio and Wyoming.
Semi-closed Primary
In a semi-closed primary, independent voters, or those without a party affiliation, may pick which party’s primary they want to cast their ballot in. However, individuals who are enrolled with a party may only cast their ballot during that party’s primary. A voter who is registered as a Democrat, for instance, may only cast their ballot in a Democratic primary. Still, a voter registered as an independent can cast their ballot in either a Democratic or Republican primary.
States with a semi-closed primary include Connecticut, Idaho, Maryland, North Carolina, Oklahoma, Oregon, South Dakota, Utah and West Virginia.
Closed Primary
A closed primary is an election in which only registered members of a particular political party can vote. In other words, a voter chooses either the Democratic Party or the Republican Party on their voter registration application and may only vote for members of that party.
Voters can only cast their ballots in a closed primary for the party with which they are enrolled. For instance, a Republican primary election is only open to voters who are registered as Republicans. In states with closed primaries, absentee voters are frequently required to select a party affiliation on their voter registration form to participate in the state’s primary elections.
States with a closed primary include Delaware, Florida, Kentucky, Nevada, New Mexico, New York and Pennsylvania.
Open to Unaffiliated Voters Primary
Many states restrict registered members of one party from voting in the primary of another, allowing only unattached voters to participate in whichever party primary they want. Because a Democrat cannot vote in a Republican Party primary or vice versa, this system is not an actual open primary.
Unaffiliated voters in New Hampshire must express their party preference at the polls to participate in that party’s primary. Unaffiliated voters in Colorado must either indicate which party they want on their ballot at the polls or return just one party’s mail ballot. Although the decision is made public, the voter’s unaffiliated status remains unchanged.
States with a primary open to unaffiliated voters include Arizona, Colorado, Kansas, Maine, Massachusetts, New Hampshire and Rhode Island.
Open Primary
A voter with any political affiliation is eligible to cast their ballot in an open primary for any party. For example, a voter who is registered as a Democrat has the option to cast a ballot in the Republican primary. Voters may only participate in one party’s primary, and many states do not require voters to declare their political allegiance when they register to vote. The way open primaries for absentee votes are conducted varies between states.
States with open primary voting include Alabama, Arkansas, Georgia, Hawaii, Michigan, Minnesota, Mississippi, Missouri, Montana, North Dakota, South Carolina, Tennessee, Texas, Vermont, Virginia and Wisconsin.
Top-Two Primary
A top-two primary system allows all candidates to run and all voters to vote in one single primary election, regardless of party affiliation, with the top-two vote getters moving on to the general election. This means that the general election could see a face-off between candidates of the same party. Washington was the first state to implement a top-two primary system for state and federal elections in 2004. California later adopted this strategy in 2010.
Other Primary Processes
Legislative elections in Louisiana and Nebraska share specific characteristics with top-two primaries, but they differ.
All candidates in Louisiana run on the same ticket on the day of the general election. If no single candidate receives more than 50% of the vote, the two candidates that receive the most votes compete in a runoff six weeks later. Another way to explain this is that there is no primary election — only a general election for all candidates — with a runoff as necessary.
Because Nebraska’s Legislature is nonpartisan, only state legislative elections are conducted using a system similar to the top-two primary system. Partisan affiliation labels are not shown next to the names of state legislative candidates. This is a process similar to local nonpartisan offices around the country.
A ballot initiative establishing a top-four primary for state executive, state legislative and congressional elections was approved by voters in Alaska in 2020. The process for a top-four primary is the same as in a top-two: All candidates are on a single ballot and all voters vote regardless of party affiliation. In a top-four primary, the top-four candidates with the most votes move on to the general election.
Presidential Candidate Selection
The presidential selection may be held in the exact same way as state election primaries and on the exact same day. However, some states do hold the presidential primary separately on either a separate day, or, sometimes, utilizing another method of candidate selection. For instance, some states use caucuses for their presidential candidate selection. According to analysis by the National Conference of State Legislatures, 39 states use the same process, while 11 states differ. In three of the states that differ — Alaska, Hawaii and North Dakota — political parties run the election.
Super Tuesday
Super Tuesday is identified as the day when the greatest number of states and territories hold their presidential primary or caucus. In 2024, those states and territories are:
- Alabama
- Alaska (Republican Party only)
- Arkansas
- American Samoa
- California
- Colorado
- Iowa (Democratic Party only)
- Maine
- Massachusetts
- Minnesota
- North Carolina
- Oklahoma
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
Why is it Important to Vote in the Primaries?
Primary elections allow the voter to select from a field of candidates who their political party is expected to nominate to run in the general election. Based on voter turnout and primary results, parties may redesign their election strategy and allocate more or less attention and resources towards certain demographics, states and issues that can serve to moderate the outcomes.