Brief State Primary Election Types

The laws governing state primaries are complex and nuanced, and state primary laws have been a cause of confusion among voters and election administrators alike. The manner in which party primary elections are conducted varies widely by state. Primaries can be categorized as closed,  partially closed,  partially open,  open to unaffiliated voters,  open or  multi-party. For a list of all 50 states and their primary types, please see the table State Primary Types at the bottom of the page. 

States often use different systems for how they conduct their state and presidential primaries: Some states hold their state and presidential primaries on the same day, some hold them weeks or even months apart, and some hold the two primaries on the same day but have different rules for each. See NCSL's How States Differentiate Presidential Primaries From State Primaries for which state primary rules differ from presidential elections. 

For more information on primary elections see the report Primaries: More Than One Way to Find a Party Nominee.   

Closed Primaries 

In general, a voter seeking to vote in a closed primary must be a registered party member. Typically, the voter affiliates with a party on their voter registration application. In states without partisan voter registration, voters who are not bona fide members of the party may face penalties. Independent or unaffiliated voters, by definition, are excluded from participating in the party nomination contests. This system deters “cross-over” voting by members of other parties and generally contributes to a strong party organization. 

 Partially Closed 

In this system, state law permits political parties to choose whether to allow unaffiliated voters or voters not registered with the party to participate in their nominating contests before each election cycle. In this system, parties may allow unaffiliated voters, while still excluding members of opposing parties. This system gives the parties more flexibility from year to year about which voters to include. At the same time, it can create uncertainty about whether certain voters can participate in party primaries in a given year.  

Partially Open 

This system permits voters to cross party lines, but their ballot choice may be regarded as a form of registration with the corresponding party. Iowa, for instance, asks voters to choose a party on the state voter registration form, yet it allows a primary voter to publicly change party affiliation for purposes of voting in a primary election. Some state parties keep track of who votes in their primaries as a means of identifying their backers. 

Open to Unaffiliated Voters 

Many states allow unaffiliated voters to participate in any party primary they choose, but do not allow voters who are registered with one party to vote in another party’s primary. This system differs from a true open primary because a Democrat cannot cross over and vote in a Republican party primary, or vice versa. New Hampshire requires that unaffiliated voters declare affiliation with a party at the polls in order to vote in that party’s primary. In Colorado, unaffiliated voters who vote by mail must return just one party’s mail ballot, or state which party ballot they want at the polls. The choice is public information, although it does not change the voter's unaffiliated status. 

Open Primaries 

In general, but not always, states that do not ask voters to choose parties on the voter registration form are “open primary” states. In an open primary, voters choose which party’s ballot to vote, but this decision is private and does not register the voter with that party. This permits a voter to cast a vote across party lines in a primary election. Critics argue that an open primary dilutes the parties’ ability to nominate. Supporters say this system gives voters maximal flexibility—allowing them to cross party lines—and maintains their privacy.  

Multi-Party Primaries (Including Top-Two and Similar Systems) 

A small but growing number of states hold a single primary in which all candidates, regardless of party, are listed on a single ballot. States vary in the number of candidates who advance out of this primary to the general election. For example, California and Washington use a “top-two” primary format in which each candidate lists his or her party affiliation or, in Washington’s case, a party “preference.” The top two vote-getters in each race, regardless of party, advance to the general election.  

Elections for Nebraska’s unicameral, nonpartisan legislature closely mirror this process except ballots do not identify the candidates’ party. (Nebraska uses open primaries for other state offices.) Alaska uses a similar system except four candidates advance to the general election instead of two.  

Advocates of the "top-two" format argue that it increases the likelihood of moderate candidates advancing to the general election ballot. Opponents maintain it reduces voter choice by making it possible that two candidates of the same party face off in the general election. They also contend it is tilted against minor parties who will face slim odds of earning a spot on the general election ballot. 

State legislative and some statewide elections in Louisiana use a modified version of this system called an “all-comers” primary; other organizations may refer to this as a “jungle” primary. In these elections, on the general election date, all candidates run on the same ticket. If no candidate receives over 50% of the vote, then the top two vote-getters face a runoff six weeks later. One way to look at this is to say there is no primary election—just a general election for all candidates, with a runoff when needed. Congressional and other offices are run through open primaries.   

 State Primary Types 

 *Maryland and Oregon use partially closed primaries, but at this time both parties choose to allow only party members to participate. 

**Louisiana uses an open to unaffiliated primary system for the following offices: state supreme court justice, State Board of Elementary and Secondary Education, and the Public Service Commission. It uses an all-comers primary system for all other state offices, including state representatives and senators. 

***Nebraska’s unicameral legislature uses nonpartisan elections that closely resemble a top-two primary system. It uses open primaries for all other state offices.