Primaries and caucuses are both methods political parties use to nominate candidates to run for office. Caucuses are systems of local gatherings in which party members decide which candidate to support, and voting is often conducted by a show of hands or other public display. Primaries, meanwhile, are statewide -- or in the case of local races, citywide -- elections held by secret ballot, similar to the general election process.

1 The Caucus Caucuses once were the most common way of nominating candidates for higher office in the United States. But over time, as the movement toward more direct democracy took root, caucuses began falling out of favor. By 1917 all but four states had abandoned caucuses as a means of electing statewide officials, though many continued to use them for presidential nominating elections until, beginning in the 1970s, presidential primaries, rather than caucuses, became increasingly commonplace. Just 10 mostly small states relied solely on caucuses for their nomination contests in the 2008 presidential election. Members of a political party from a precinct, district or county gather to debate and select delegates to represent candidates for either the party's county or state convention in a caucus. Even though caucuses are open to all members of a political party, turnout is usually quite low because caucuses are so time-consuming, which gives party leaders and activists greater say in whom the caucus supports.

2 The Primary In a primary, voters go to their polling station, as they would for a general election, and are presented with a list of the candidates running for office from a specific political party. They then choose the candidate they support. The candidate with the most primary votes wins. There are a few different types of primary. In a closed primary, only declared members of a political party may vote in that party's nominating contest. In an open primary, however, voters may choose the party primary in which they would like to vote. Some states have adopted mixed systems, in which independents may select which primary they'd like to vote but declared members of a political party can only vote in that party's primary.

3 Advantages of Caucuses Caucuses, though they tend to have lower turnouts -- with the exception of the Iowa caucuses, which kickstart every presidential election season -- are said to be advantageous in that they allow for a more grassroots style of campaigning, giving candidates who perhaps do not have as much money or name recognition the chance to be competitive. In presidential elections, because most of the states that still hold caucuses are small and tend to be ignored by national candidates, caucuses can reward those, like Barack Obama in 2008, who focus resources on convincing their supporters to participate.