The alternative vote, commonly abbreviated AV, is a preferential plurality or majority electoral system used in single-member districts. Voters rank candidates according to preference, usually marking a first choice followed by second, third and subsequent choices. International IDEA defines AV as a system in which a candidate who receives an absolute majority of valid first-preference votes is elected immediately.
If no candidate reaches an absolute majority, the least successful candidate is eliminated and that candidate's votes are transferred according to the next available preferences until one candidate has an absolute majority. AV is therefore designed to produce a majority winner without requiring a second election day. It achieves this by using one preferential ballot and successive redistribution of preferences rather than by holding a separate runoff election. The system is sometimes called instant-runoff voting because the successive counting stages perform a function comparable to repeated runoff contests within one election process.
The counting procedure begins by counting every voter's first preference. If one candidate obtains more than half of the valid first preferences, that candidate wins and no further count is necessary. If nobody reaches the required majority, the candidate with the fewest votes is eliminated. Ballots that ranked the eliminated candidate first are examined for their next available preference, and those preferences are transferred to the remaining candidates. The totals are then recalculated.
If a candidate now has an absolute majority, that candidate wins; otherwise another candidate is eliminated and the process continues. Ballots can eventually become exhausted if a voter has not expressed a preference among any remaining candidates, depending on the ballot rules. The essential mechanism is therefore sequential elimination combined with transfer of later preferences until one candidate obtains the required majority.
AV is a single-member system, which is the most important distinction between it and STV. In AV, only one candidate can win the district, so there is no quota for electing several representatives. The majority threshold is achieved through transfers rather than through a multi-member proportional allocation. STV, by contrast, uses multi-member districts and a quota to elect several candidates.
Both systems can use ranked ballots and both can transfer votes, but they belong to different electoral-system families in terms of the representation they produce. AV is classified by International IDEA as a plurality or majority system, while STV is classified as a proportional representation system. Thus, the presence of transferable preferences does not itself make an electoral system proportional. District magnitude and the method of converting preferences into seats are crucial to the classification.
AV changes the meaning of a voter's later preferences because those preferences can become electorally relevant if earlier choices are eliminated. A voter can therefore support a preferred candidate first without necessarily treating the vote as wasted if that candidate has insufficient support to survive the count. The voter can rank another candidate second and potentially influence the final contest. The system consequently permits voters to express a sequence of preferences rather than selecting only one candidate.
However, voters are not required in every implementation to rank every candidate, and the treatment of incomplete rankings depends on electoral law. A ballot with only a first preference can become exhausted after that candidate is eliminated if no further preference is available. This makes ballot instructions and voter understanding important components of the practical operation of AV.
AV is sometimes described as a majority system because its winning candidate must obtain more than half of the continuing valid vote at the decisive stage. This should not be confused with the claim that the winner necessarily receives more than half of all first preferences. A candidate can win after receiving fewer than half of the first preferences because transfers from eliminated candidates subsequently give that candidate a majority among the votes that remain transferable.
The distinction between first-preference support and final transferred support is therefore fundamental. AV does not require a separate second election, unlike a conventional two-round system. Instead, the electorate casts one ranked ballot and the alternative count effectively simulates successive runoff stages. International IDEA explicitly distinguishes AV from the Two-Round System even though both can be used to produce a majority winner.
The system has important implications for electoral strategy because candidates can benefit from being acceptable as later preferences among voters whose first choice is eliminated. Parties and candidates may therefore have incentives to appeal beyond their core supporters, although the actual strategic effects depend on political competition, voter behaviour and the number of candidates. Voters may rank candidates sincerely according to their preferences or may consider which candidates are likely to survive successive eliminations.
The system can also produce situations in which the final winner was not the first-preference leader because transfers changed the relative standings. These properties distinguish AV from first-past-the-post, where only first-choice votes normally determine the winner. The system therefore changes both the information expressed by the ballot and the way electoral support is accumulated during the count.
AV has been used nationally in Australia for the House of Representatives and is included by International IDEA among the major plurality and majority electoral systems. It has also been used in other jurisdictions and at subnational levels, while related ranked-ballot systems appear under different names. The precise ballot requirements and counting procedures can differ, particularly concerning exhausted ballots, compulsory numbering and treatment of informal ballots.
AV is consequently a technical electoral-system category rather than a single identical ballot design worldwide. International IDEA's comparative database identifies Australia as using AV for its national legislature and distinguishes AV from both STV and Two-Round Systems. These classifications demonstrate that the system is defined by the combination of a single-member district, preferential voting and elimination and transfer until a majority is obtained.
The alternative vote is therefore a single-member preferential majority system in which voters rank candidates and later preferences are transferred whenever no candidate has an initial majority. Its defining characteristics are one seat per district, preferential voting, elimination of the lowest placed candidate and redistribution of transferable preferences until a candidate obtains the required majority.
It differs from first-past-the-post because later preferences can matter, from STV because only one representative is elected, and from a two-round system because the successive runoff stages occur through one ballot and one counting process rather than through separate elections. It also differs from general preferential voting as a broad category because AV is one particular preferential electoral system with a specific single-member majority structure.
