By-election

A by-election, also known as a special election in the United States and the Philippines, a bye-election in Ireland, a bypoll in India, or a Zimni election (Urdu: ضمنی انتخاب, supplementary election) in Pakistan, is an election used to fill an office that has become vacant between general elections.

A vacancy may arise as a result of an incumbent dying or resigning, or when the incumbent becomes ineligible to continue in office (because of a recall, election or appointment to a prohibited dual mandate, criminal conviction, or failure to maintain a minimum attendance), or when an election is invalidated by voting irregularities. In some cases a vacancy may be filled without a by-election or the office may be left vacant.

Origins

The procedure for filling a vacant seat in the House of Commons of England was developed during the Reformation Parliament of the 16th century by Thomas Cromwell; previously a seat had remained empty upon the death of a member. Cromwell devised a new election that would be called by the king at a time of the king's choosing. This made it a simple matter to ensure the seat rewarded an ally of the crown.

During the eighteen-year Cavalier Parliament of Charles II, which lasted from 1661 to 1679, by-elections were the primary means by which new members entered the House of Commons.

In single-member constituencies

By-elections are held in most nations that elect their parliaments through single-member constituencies, whether with or without a runoff round. This includes most Commonwealth countries, such as the United Kingdom, Canada, Australia and Pakistan, as well as non-Commonwealth countries such as France and Italy (until 2006).

In the United States, these contests have been called "special elections" because they do not always occur on Election Day like regular congressional elections. Special elections are held when a seat in the House of Representatives, state legislature, or local legislature becomes vacant. At the federal level, the U.S. Constitution requires that vacancies in the House of Representatives be filled with a special election (unlike the Senate, where it is up to law of the state involved to determine how the vacancy is filled). In most cases where a vacancy is filled through a special election, a primary will also be held to determine which candidates will represent the major parties.

In multi-member constituencies

When one seat in a multi-member constituency becomes vacant, the consequences vary. For example, a by-election may be held to fill just the vacancy, all the seats in the constituency could be contested in the by-election, or the vacancy could be filled by other means.

Typically, party-list proportional representation systems do not hold by-elections. Instead, the most successful unelected candidate named on the vacator's list fills the vacancy automatically. However, Turkey is an exception, as it holds by-elections when too many seats become vacant in the parliament (as in 1986) or a repeat vote has to be held (as in 2003).

In multi-member district systems that do not employ party lists - single transferable vote, single non-transferable vote and plurality at-large - vacancies may be filled by a by-election. This is done, for example, in the Dáil of the Republic of Ireland (STV), in the Parliament of Vanuatu (SNTV), and in the Senate of the Philippines (Pl. AL). In those systems, alternatives to holding a by-election include:

# re-determining the election results with the vacators disregarded, as in Tasmania or the Australian Capital Territory,
# keeping the seat vacant until the next general election. This usually occurs if a vacancy arises shortly before a planned general election (within six months in New Zealand).
# nominating another candidate with the same affiliation as the former member, such as European Parliament seats in the Republic of Ireland.

For the Australian Senate (in which each state forms a multi-member constituency elected via single transferable vote), the state parliament appoints a replacement in the event of a vacancy; in 1977 a referendum amended the Constitution to require that the person appointed must belong to the same