Single-member district plurality

Plurality voting is an electoral system in which each voter is allowed to vote for only one candidate, and the candidate who polls the most among their counterparts (a plurality) is elected. In a system based on single-member districts, it may be called first-past-the-post (FPTP), single-choice voting, simple plurality or relative/simple majority. In a system based on multi-member districts, it may be referred to as winner-takes-all or bloc voting. The system is often used to elect members of a legislative assembly or executive officers. It is the most common form of the system, and is used in Canada, the lower house (Lok Sabha) in India, most elections in the United Kingdom (excluding some Scottish and Northern Irish elections), and most elections in the United States.

Plurality voting is distinguished from a majoritarian electoral system, in which, to win, a candidate must receive an absolute majority of votes—i.e. more votes than all other candidates combined. Both systems may use single-member or multi-member constituencies, In the latter case it may be referred to as an exhaustive counting system: one member is elected at a time and the process repeated until the number of vacancies is filled.

In some countries such as France (as well as in some jurisdictions of the United States, such as Louisiana and Georgia) a "two-ballot" or "runoff election" plurality system is used. This may require two rounds of voting. If on the first round no candidate receives over 50% of the votes, then a second round takes place, with just the two highest-voted candidates in the first round. This ensures that the winner gains a majority of votes in the second round. Alternatively, all candidates above a certain threshold in the first round may compete in the second round. If there are more than two candidates standing, then a plurality vote may decide the result.

In political science, the use of plurality voting with multiple, single-winner constituencies to elect a multi-member body is often referred to as single-member district plurality or SMDP. This combination is also variously referred to as winner-takes-all to contrast it with proportional representation systems. This term is sometimes also used to refer to elections for multiple winners in a particular constituency using bloc voting.

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