Types of Primaries in the U.S.

Paul Rader
7 min readDec 6, 2018

UPDATE 12/7/2021: I have recently written and self-published my own book! It’s called Why Independents Rarely Win Elections: And How They Could Become More Competitive. It is a comprehensive look at the reasons why independent candidates for elected office have such a tough time being successful, and provides some practical measures that can be taken to make them more viable in elections. You can buy it here at Amazon as an ebook or paperback! And if you enjoy it, please leave a review!

Image source: WILX 10. “How Much Will Your Primary Vote Matter?” https://www.wilx.com/home/headlines/How-Much-Will-Your-Primary-Vote-Matter-370852931.html

There are multiple types of primaries used throughout the U.S. to determine general election candidates, and each state has their own types of primaries that they use for different levels of government. How each one works can have major implications for how elections play out. Primaries also may or may not have provisions for run-off voting if a candidate fails to win enough votes the first time around.

Below we will discuss the major types of primaries. At the end of this article are resources for more information on this topic. Also, note that sometimes minor parties will have a certain type of primary in a state, but there are some states that do not even recognize these minor parties as official parties. There are also some cases where parties use conventions in conjunction with or instead of primaries, where delegates nominate a candidate to be the party’s representative or a slate of candidates to be voted on in a primary.

Closed Primaries

How does it work?: Voters can only vote for a party if they registered with that party. Unaffiliated voters cannot participate in a party’s primary and, as a result, can only vote in nonpartisan races when it is a primary election. In a few states with closed primaries, not every party will require registration with them to participate in their primary.

Effects: Closed primaries often (though not always) see more strongly partisan and/or ideological candidates running, or at least candidates who make such appeals. Primaries see much less turnout than general elections, and those that do vote in primaries tend to be more partisan and ideological than those voters in general elections.

Where is it used?: There are 14 states where at least one party holds a closed primary for congressional and state-level offices, and 11 of these states have them for all of their political parties.¹ It is not always required for every party in a state to have the same type of primary.

Open Primaries

How does it work?: Voters can pick whatever party’s primary to participate in, regardless of affiliation (or if they are unaffiliated). Voters choose which primary to participate in privately. Thus, Republicans can vote in Democratic primaries and Democrats can vote in Republican primaries if they wish. Note that in many, if not all, of these states, voters do not actually register under a particular affiliation.

Effects: Since voters can choose to vote in either party, there will generally (but not always) be more centrist and moderate candidates running than in a closed primary election.

Where is it used?: There are 22 states where at least one political party has open primaries for its congressional and state-level offices, with 20 of them having open primaries for all political parties.¹ Some of these states use semi-open primaries, which are mostly the same thing (more on that further below).

Semi-closed Primaries

How does it work?: If a voter is affiliated with a particular party, that voter must vote in that party’s primary. However, unaffiliated voters can choose which party’s primary to vote in (as long as a political party’s officials allow this).

Effects: It is much more ambiguous whether more partisan/ideological or centrist/moderate candidates benefit more from semi-closed primaries compared to closed and open primaries. The divide between Republican and Democratic voters and the proportion of independent/third-party voters tends to be a more important consideration in this type of primary (though that is not to say that it isn’t important in closed or open primaries, of course).

Where is it used?: There are 15 states that have semi-closed primaries for at least one political party, and 12 of them use semi-closed primaries for all political parties.¹

Semi-Open Primaries

How does it work?: These work similarly to an open primary, where voters can choose which party’s primary to participate in. However, instead of being a private matter the choice of a party’s ballot has to be publicly declared.

Effects: The effects of semi-open primaries are generally similar to open primaries, as they basically function the same way.

Where is it used?: Of the states mentioned above in the open primary section, six of those use semi-open primaries: Illinois, Indiana, Iowa, Ohio, Tennessee, and Wyoming.²

Ranked-Choice Primaries

How does it work?: As the name implies, choices are picked according to what order of preference voters would like to win the election. If a candidate receives over half the vote in the first round, he or she is the winner and the preference ranking doesn’t matter. If this does not happen, the candidate with the least first-place votes is eliminated, and the second-place votes are counted next. If there is still no majority winner when the second-round votes are added, the third-place votes are counted, and so on. The election winner is declared by the time a round results in them capturing over half the vote.

Effects: The effects of ranked-choice primaries are ambiguous, depending on the nuances of each district that uses them. It is hard to say whether it is a generally better strategy to run as a more partisan/ideological candidate than a centrist/moderate.

Where is it used?: The vast majority of ranked-choice voting (RCV) occurs at the municipal level of some states, and sometimes only for certain cities. The most notable instance now is Maine’s use of it for its gubernatorial primaries in 2018, the first time for that particular type of election in the state.

Top-Two Primaries

How does it work?: All candidates for an office are listed on the ballot, regardless of their party affiliation or if they have no affiliation. The two candidates who win the most votes move on to the general election to face-off against each other.

Effects: The effects of top-two primaries depend in large part on the number of candidates running and how many each party puts up for election. Districts will sometimes see either two Democrats or two Republicans duke it out in general elections. Having two candidates of the same major party can often result out of a large crowd of candidates from the other major party, as that party’s votes will be much more split among its candidates. For example, if six Democrats ran compared to two Republicans in a district, a couple of the Democrats that may have normally been more likely to move to the general election may see would-be votes for them be split among the other four Democrats to give them less than what the two Republicans got in the primary.

Where is it used?: There are only three states that use top-two primaries for at least state legislative elections: California, Washington, and Nebraska.¹ California and Washington also use them for congressional elections and are the more noted states for their top-two primaries compared to Nebraska.

Jungle Primaries

How does it work?: Like with top-two primaries, all candidates for an office are listed on the ballot. But unlike a top-two primary, a candidate in a jungle primary can win outright if they capture a majority of the vote the first time. If no candidate wins a majority, then the top two finishers go to a run-off. Thus, many times a jungle primary will function basically like a top-two primary.

Effects: The effects of jungle primaries are similar to top-two primaries, although the former has the chance to declare a winner outright in the primary.

Where is it used?: As far as I know (I cannot confirm definitively, but I’m 99% sure), Louisiana is the only state that uses a jungle primary. Sometimes, top-two primaries are erroneously referred to as jungle primaries. Even though they are both very similar, the key difference is that the election can be won outright in a true jungle primary if the top vote-getter has a majority of the votes cast.

One more note to emphasize: The effects of each type of primary listed above are general rules of thumb. Campaign strategies are much more complex and have to take into account many other factors for each district or state. For example, it may actually be a better strategy in a closed primary to run as a more centrist/moderate candidate than a more partisan/ideological one. But it is usually a better idea to be the latter than the former for closed primaries.



Paul Rader

Nonpartisan political analyst, researcher, and speaker; self-published author; bridging political divisions and closing gaps in civic knowledge