A primary election is conducted so that voters can select candidates for a subsequent election (this is called the nominating primary). Prior to general elections, the primaries allow for each political party to decide its nominee for the upcoming general election.

Numbered years, 2012, 2014 etc., are federal general election years, so many states hold both presidential preference primaries to select the presidential candidates, and state primaries to select federal congressional candidates.

Primaries work in different ways and are classified by various categories:

• Open: Voters may vote in primaries of a party of their choice – this choice will be made at the voting booth. In other words, you can choose which party's primary to vote in, regardless of your own party affiliation or lack thereof. You CANNOT, however, vote in more than one party primary - you must choose one, and only one, party’s primary in which to vote.
• Closed: Voters must declare party affiliation in advance of the primary election and can only vote in that party's primary. To participate in your party's closed primary election, you must identify party affiliation when you register to vote.
• Semi-closed: Voting is restricted to voters who have already declared their affiliation to the party in advance and new and/or independent (non-affiliated voters) who choose which primary to vote in on Election Day. To participate in your party's semi-closed primary election, you must identify party affiliation when you register to vote.
• Semi-open: Voters can choose which party's primary to vote in on Election Day, regardless of their party affiliation, but must do so publicly.