Primaries and caucuses are methods that political parties use to select candidates for a general election. Here are some details on the two election methods.
What are primaries?
A primary is a state-level election where party members vote to choose a candidate affiliated with their political party. Party candidates selected in a primary then run against each other in a general election. Thirty-four U.S. states conduct primary elections.
There are several types of primaries in the U.S. system.
Closed primary: Participation is open only to a particular political party’s registered members. Independents or other party members cannot participate.
Semi-closed primary: Participation is open to registered party members and unaffiliated voters. State election rules determine whether unaffiliated voters may make their choice of party primary in the privacy of the voting booth or in public by registering with a party on Election Day.
Open primary: Any registered voter may participate in any party primary.
Semi-open primary: Any registered voter may participate in any party primary but when they identify themselves to election officials they must request a party’s specific ballot.
Here's a calendar of primaries and caucuses in the 2012 presidential election.
What are caucuses?
A caucus is a local meeting where registered members of a political party in a city, town or county gather to vote for their preferred party candidate and conduct other party business. Caucuses typically are used in combination with a state convention to elect delegates to the national nominating convention for presidential elections.
The caucus is the oldest method of choosing delegates in the U.S., widely acknowledged as originating in the English colonies before the American Revolution. Sixteen states hold caucuses to determine political party candidates. Iowa holds the first, and most significant, caucuses in the presidential election cycle. More info on the Iowa caucuses can be found in the Drake University field guide to the Iowa caucuses.