Exhaustive ballot

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The exhaustive ballot is a voting system used to elect a single winner. Under the exhaustive ballot the elector casts a single vote for his or her chosen candidate. However, if no candidate is supported by an overall majority of votes then the candidate with the fewest votes is eliminated and a further round of voting occurs. This process is repeated for as many rounds as necessary until one candidate has a majority.

The exhaustive ballot is similar to the two-round system but with key differences. Under the two round system if no candidate wins a majority on the first round, only the top two recipients of votes advance to the second (and final) round of voting, and a majority winner is determined in the second round. By contrast, on the exhaustive ballot only one candidate is eliminated per round; thus, several rounds of voting may be required until a candidate reaches a majority. (In some circumstances, the two or more lowest candidates can be eliminated simultaneously if together they have fewer votes than the lowest candidate above them. In other words, this "bulk exclusion" cannot change the order of elimination, unlike a two-round system.)

Because voters may have to cast votes several times, the exhaustive ballot is not used in large-scale public elections. Instead it is usually used in elections involving, at most, a few hundred voters, such as the election of a prime minister or the presiding officer of an assembly. The exhaustive ballot is currently used, in different forms, to elect the members of the Swiss Federal Council, the First Minister of Scotland, the President of the European Parliament, and the speakers of the House of Commons of Canada, the British House of Commons and the Scottish Parliament, the host city of the Olympic Games and the host of the FIFA World Cup, and, formerly, to elect the President and the State Comptroller of Israel, which are now elected—though still indirectly by the Knesset—using a two-round system.