What's the Difference Between a Caucus and a Primary?

By: Dave Roos  | 
Iowa caucus
Democratic presidential candidate, former Vice President Joe Biden speaks during an event in Fort Dodge, Iowa, two before the Iowa caucus. Al Drago/Getty Images

Every four years, television news crews from New York to Los Angeles set up camp in the frigid cornfields of rural Iowa. The Iowa Caucuses, held in early February, represent the first chance for regular Americans from both major political parties to show support for a presidential candidate. The national press covers every minute of pre-caucus excitement as presidential hopefuls spread out across all 99 Iowa counties to shake hands at local diners and give stump speeches in elementary school gyms.

As the earliest event of the primary election season — you know, the free-for-all that determines the nominees in each party — Iowa serves as a bellwether of national sentiment, helping to launch or sink candidacies and separate the wheat from the chaff — or in Iowa's case, the corn from the husk. But what exactly is a caucus? And how is it different from a primary?


Caucuses and primaries are the two ways in which the Democratic and Republican parties choose the delegates who will attend the parties' national conventions. The national convention is where the delegates officially choose the party's nominee for the presidential race.

Primaries offer a relatively straightforward way of assigning delegates to the national convention. Voters from each party cast their vote for one of the candidates on the primary ballot. Like the general presidential election, primary voting is done on an assigned day at an assigned polling place. Voting is private and anonymous. Depending on the state's rules, delegates are either distributed in proportion to the amount of votes received by each candidate (known as a proportional primary), or all delegates are given to the candidate who gets the most votes (called a "winner take all" primary).

Caucuses, on the other hand, are far from straightforward. (Interestingly, before the 1960s and 1970s, most states chose their delegates through caucuses, not primaries.) For one thing, caucuses aren't exclusively for presidential elections. In addition, caucuses were traditionally held every two years so that local members of each political party could meet, discuss the issues of the day, and help to shape the political platform of the state and national party [source: Redlawski et al].

How do caucuses and primaries function today? Find out next.


Modern Caucuses and Primaries

The caucus process hasn't changed much at all since each party began nominating their choices for president at their national conventions in the early 19th century. In Iowa, for example, voters in each local precinct (there are around 1,700) gather in gyms, bars and basements to openly discuss the presidential election, not just vote for a specific candidate [source: Praetorius]. Supporters give impassioned speeches on behalf of their candidate, attempting to sway the undecided folks in the room. Unlike primaries, caucuses are held at a specific time of the day, the only time when voters can cast their ballot. In fact, there don't even have to be official ballots. Local caucus organizers can simply call for a show of hands, or ask folks to divide into groups according to their candidate.

It's important to note that the results of local caucuses don't directly influence the proportion of delegates sent by each party to the national convention. Instead, delegates are chosen through a multi-stage, months-long process. In Iowa, for example, the precinct caucuses help to portion out delegates for the county conventions, which help to choose delegates for the district conventions, which vote to choose delegates for the state convention, which finally chooses the delegate distribution for the national convention. To further confuse matters, the Republican and Democratic Iowa caucuses each have different rules governing the distribution of delegates and whether or not votes cast in each stage of the process are even binding.


Several states hold both a primary and caucuses, although only one of the contests results in the selection of delegates. Non-binding caucuses and primaries are sometimes called straw polls, or the more colorful term, "beauty contests" [source: Seelye]. Most states opt for primaries with only Iowa, Kentucky, Nevada, North Dakota and Wyoming relying solely on caucuses [source: FactCheck].

For lots more information about U.S. elections and political controversies, explore the related links below.


Originally Published: May 1, 2012

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  • PBS NewsHour. "The Primary versus the Caucus." December 15, 2003 (April 24, 2012) http://www.pbs.org/newshour/vote2004/primaries/sr_primary_caucus.html
  • Praetorius, Dean. The Huffington Post. "What Is a Caucus? How the Iowa Caucus Works." January 3, 2012 (April 24, 2012) http://www.huffingtonpost.com/2012/01/03/what-is-a-caucus-iowa-2012_n_1181069.html
  • Redlawski, David P.; Tolbert, Caroline J.; and Donovan, Todd. Why Iowa? Why Caucuses and Sequential Elections Improve the Presidential Nominating Process. "Iowa Caucus Rules." University of Chicago, 2011. http://www.whyiowa.org/Why Iowa Chapter 3.pdf
  • Seelye, Katherine Q. The New York Times. "Romney's Victory in the Maine Caucuses Is at Risk." February 16, 2012 (April 23, 2012) http://thecaucus.blogs.nytimes.com/2012/02/16/romneys-victory-in-the-maine-caucuses-is-at-risk/
  • The Takeaway. "What's the Difference Between a Caucus and a Primary?" February 7, 2012 (April 22, 2012) http://www.thetakeaway.org/2012/feb/07/whats-difference-between-caucus-and-primary/
  • Washington State Democrats. "2012 Caucuses and Conventions" (April 24, 2012) http://www.wa-democrats.org/caucuses