A primary is an election run by the state: you vote by secret ballot during polling hours, and often early or by mail. A caucus is a meeting run by a political party: you show up at a set time and place, and participants vote, sometimes in public, after speeches. Both choose delegates to the parties’ national conventions, but primaries draw far more voters, which is why most states have abandoned caucuses for presidential nominations.
How does a primary work? #
A presidential primary works like any other election. The state and counties run it, poll workers staff it, and you cast a secret ballot at your polling place, by mail or during early voting. Results allocate each party’s delegates to candidates under party rules. Our explainer on how pledged delegates are allocated covers the math.
Who can vote depends on the state’s rules: closed, open or somewhere in between. See open vs. closed primaries. Because a primary takes a few minutes and offers flexible hours, turnout is much higher than at caucuses.
How does a caucus work? #
A caucus is organized and paid for by the state party. Participants gather at a set time, usually a weekday evening, in schools, churches, libraries and community centers across the state.
Republican caucuses #
Typically, supporters give short speeches for each candidate, then participants vote by secret paper ballot. Votes are counted on the spot and reported to the state party. The ballot is private, but you still have to be there at the scheduled time.
Democratic caucuses #
The traditional Democratic caucus, famous in Iowa, was public. Participants stood in groups by candidate. Any group under a viability threshold, usually 15% of the room, was eliminated, and its members could join another group in a second round. That “realignment” rewarded organization and second-choice appeal, but it took hours and excluded people who couldn’t attend.
After Iowa’s 2020 Democratic caucus results were delayed for days by a failed reporting app, the national party pushed states away from in-person caucuses. In 2024, Iowa Democrats ran a mail-in process instead, with results released on March 5.
Primaries vs. caucuses side by side #
| Primary | Caucus | |
|---|---|---|
| Run by | State and county election officials | State political party |
| How you vote | Secret ballot; often early and mail options | In person at a set time; public or paper ballot depending on party |
| Time needed | Minutes | An hour or more |
| Turnout | Higher | Much lower |
| Paid for by | Taxpayers | The party |
| Accessibility | Absentee, early voting, disability access required by law | Hard for shift workers, parents, people with disabilities, service members abroad |
Why caucuses reward organization #
In a primary, a campaign reaches voters mainly through ads, mail and digital outreach. In a caucus, the job is to get committed supporters to a specific room on a specific night, and in the traditional Democratic format, to have someone persuade neighbors face to face. Candidates with passionate, well-organized support have often outperformed their statewide poll numbers in caucuses. Candidates who are broadly liked but lightly supported do better in primaries.
That’s also why caucuses are hard to poll. With low, uneven turnout, a pollster has to guess who will spend a winter evening in a gym, and small errors in that guess produce big misses.
Which states still use caucuses? #
Fewer every cycle. In 2024 the Republican contests in Iowa, Nevada, Idaho, Missouri, North Dakota, Utah, Wyoming and Hawaii were caucuses or party-run contests rather than state primaries, along with several territories. Michigan Republicans used a hybrid of a primary and a party convention.
Two quirks show how messy the system can be:
- Nevada held a state-run primary on February 6, 2024, but the state Republican Party awarded its delegates through its own caucus two days later.
- Idaho eliminated its presidential primary in 2023, intending to move it, but the replacement bill failed. Both parties caucused in 2024.
On the Democratic side, 2024 caucuses were limited to a handful of states, including Iowa (by mail), Hawaii, Alaska, Wyoming and Idaho, plus territories. States such as Colorado, Minnesota, Maine and Washington switched from caucuses to primaries in recent cycles.
What about 2028? #
The 2028 calendar is taking shape now. In August 2026 the Democratic National Committee approved an early-state window with South Carolina first on January 22, 2028, followed by Nevada, New Hampshire, New Mexico and Michigan in February. Iowa Democrats were not included in the early window. Republicans have signaled they’ll keep a traditional order with the Iowa caucuses first. Dates can still shift as states pass laws and parties finalize rules. Our guide to when the 2028 presidential primaries begin tracks the calendar, and our explainer on front-loading covers why states compete to go early.
National polls of the 2028 fields are already appearing. Election Tracker, our free iPhone app, has a 2028 Primary tab with separate Republican and Democratic fields, each with a 30-day polling average and a trend line. Every poll lists its pollster, sample size, population and dates, which matters this early, when many polls survey all adults rather than likely primary voters.
Frequently asked questions #
Do caucus and primary voters vote directly for the candidate? #
Not quite. In both, the results allocate delegates pledged to candidates, and those delegates formally choose the nominee at the national convention. In practice, the candidate who wins a majority of pledged delegates is the nominee.
Why do Iowa and New Hampshire traditionally go first? #
Iowa’s caucuses moved early in the 1970s, and New Hampshire has long held the first primary, which its state law protects. Both became traditions that shaped campaigns for decades. Democrats have since moved other states ahead of them; Republicans have kept the traditional order.
Can independents participate in caucuses? #
Usually only if they register with the party, sometimes on the spot. Caucuses are party events, so parties set the rules, and many require participants to be registered members.
Why did states switch from caucuses to primaries? #
Turnout and access. Caucuses exclude people who can’t attend at a fixed time, and they’ve produced reporting problems, most famously in Iowa in 2020. Primaries are run by election officials with established procedures.