In democratic political systems the selection of candidates is critically important as political parties and the party preferences of voters have come to dominate electoral politics. Party selection of candidates thus effectively determines the public's choice of who will represent them. In electoral areas which are dominated by a single party, that party's choice of candidate also then effectively determines who is elected.
In Britain and Europe the political parties are responsible for selecting their candidates. This is done on either a local, regional, or national basis. Britain's first‐past‐the‐post electoral system has in the past facilitated localized constituency party selection. Here, the ‘selectorate’ may be limited to branch delegates or a local party electoral college, but most parties have now embraced the principle of one member one vote (OMOV). The national party role may involve simply routine endorsement of local party decisions. However, in recent years central party involvement has increased primarily so as to vet potential candidates' ability to withstand media scrutiny and support party views. Central party intervention has been the greatest in the Labour Party to ensure better female representation. This resulted in the practice of imposed all‐women shortlists, made legal by legislation allowing positive discrimination in 2002.
In countries where list elections are held either on their own or as part of mixed member electoral systems, candidate selection focuses not simply on the selection of candidates but on their ranking on party lists. Historically, list selection has been associated with greater central party influence over selection and ranking. Although this has been diluted by recent trends towards party democratization, in list selection too there is evidence of central party intervention to ensure better female representation. In Britain, Plaid Cymru innovated in ‘zipping’ list candidate selection for the National Assembly for Wales by placing a woman at the top of each of their regional lists, followed by a man, another woman, and so on.
In some political systems parties have involved the electorate directly in candidate selection. In part of the United States a system of primary elections was introduced in the late nineteenth and early twentieth centuries to overcome the corruption which had developed through selection by party convention or caucus. The primary election transfers responsibility for selecting the candidate from the party to the electorate: either the electorate at large or those members of the electorate who have registered with the public authorities as supporters of the party. Moreover, the primary election is part of the official business of government; it ceases to be part of an internal party process and the party has to accept the outcome of the primary election. Primaries are held to establish candidates both for the Congress (both Houses) and, on a loosely organized state‐by‐state basis, for presidential elections.