A primary election is an election that narrows the field of candidates before an election for office. Primary elections are one means by which a political party or a political alliance nominates candidates for an upcoming general election or by-election.
Primaries are common in the United States, where their origins are traced to the progressive movement to take the power of candidate nomination from party leaders to the people.
Other methods of selecting candidates include caucuses, conventions, and nomination meetings. Historically, Canadian political parties chose their candidates through nominating conventions held by constituency riding associations. Canadian party leaders are elected at leadership conventions, although some parties have abandoned this practice in favor of one member, one vote systems.
Where primary elections are organized by parties, not the administration, two types of primaries can generally be distinguished:
* ''Closed primary''.〔(【引用サイトリンク】title=Closed Primary Election Law & Legal Definition )〕 (synonyms: internal primaries, party primaries) In the case of closed primaries, internal primaries, or party primaries, only party members can vote.
* ''Open primary''.〔(【引用サイトリンク】title=Open Primary Law & Legal Definition )〕 All voters can take part in an open primary and may cast votes on a ballot of any party. The party may require them to express their support to the party's values and pay a small contribution to the costs of the primary.
In the United States, other types can be differentiated:
* ''Closed primary''. People may vote in a party's primary only if they are registered members of that party prior to election day. Independents cannot participate. Note that because some political parties name themselves independent, the terms "non-partisan" or "unaffiliated" often replace "independent" when referring to those who are not affiliated with a political party. Thirteen states — Connecticut, Delaware, Florida, Kentucky, Maine, Nebraska, Nevada, New Jersey, New Mexico, New York, Oklahoma, Pennsylvania, and South Dakota — have closed primaries.
* ''Semi-closed''. As in closed primaries, registered party members can vote only in their own party's primary. Semi-closed systems, however, allow unaffiliated voters to participate as well. Depending on the state, independents either make their choice of party primary privately, inside the voting booth, or publicly, by registering with any party on Election Day. Thirteen states — Alaska, Arizona, Colorado, Iowa, Kansas, Massachusetts, New Hampshire, North Carolina, Oregon, Rhode Island, Utah, West Virginia, and Wyoming — have semi-closed primaries that allow voters to register or change party preference on election day.〔
* ''Open primary''. A registered voter may vote in any ''party primary'' regardless of his own party affiliation. When voters do not register with a party before the primary, it is called a ''pick-a-party primary'' because the voter can select which party's primary he or she wishes to vote in on election day. Because of the open nature of this system, a practice known as raiding may occur. Raiding consists of voters of one party crossing over and voting in the primary of another party, effectively allowing a party to help choose its opposition's candidate. The theory is that opposing party members vote for the weakest candidate of the opposite party in order to give their own party the advantage in the general election. An example of this can be seen in the 1998 Vermont senatorial primary with the nomination of Fred Tuttle as the Republican candidate in the general election.
* ''Semi-open''. A registered voter need not publicly declare which political party's primary that they will vote in before entering the voting booth. When voters identify themselves to the election officials, they must request a party's specific ballot. Only one ballot is cast by each voter. In many states with semi-open primaries, election officials or poll workers from their respective parties record each voter's choice of party and provide access to this information. The primary difference between a semi-open and open primary system is the use of a party-specific ballot. In a semi-open primary, a public declaration in front of the election judges is made and a party-specific ballot given to the voter to cast. Certain states that use the open-primary format may print a single ballot and the voter must choose on the ballot itself which political party's candidates they will select for a contested office.
* ''Blanket primary''. A primary in which the ballot is not restricted to candidates from one party.
* ''Nonpartisan blanket primary''. A primary in which the ballot is not restricted to candidates from one party, where the top two candidates advance to the general election regardless of party affiliation. California has used a nonpartisan blanket primary since 2012 after passing Proposition 14 in 2010, and Washington has used a nonpartisan blanket primary since 2008.
* ''Unified Primary''.〔(【引用サイトリンク】title=The Unified Primary Election System )〕〔(【引用サイトリンク】title=Electoral System Summary )〕〔(【引用サイトリンク】title=The Unified Primary: A New Way to Conduct Nonpartisan Elections )〕 A nonpartisan primary where voters may choose any number of candidates regardless of party. The top two candidates selected the most advance to the general election regardless of party affiliation.
There are also mixed systems in use. In West Virginia, where state law allows parties to determine whether primaries are open to independents, Republican primaries are open to independents, while Democratic primaries were closed. However, as of April 1, 2007, West Virginia's Democratic Party opened its voting to allow "individuals who are not affiliated with any existing recognized party to participate in the election process."
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