Instant runoff voting (IRV) is a winner-take-all system that both protects majority rule and allows minority participation. It is a sensible alternative to both the plurality voting system and the two-round runoff system used in most American elections for offices held by a single representative, such as a president, governor, mayor or district representative.

In plurality voting, a voter casts one vote for a candidate, and the candidate who obtains the most votes wins the election. If more than two candidates run, however, the winner may receive less than 50 percent of the vote, and one of the candidates may be perceived as a "spoiler." In two-round runoffs, the top two candidates face off in a second of rounding to produce a majority winner. But runoffs are expensive for both taxpayers and candidates who must pay for two elections. Instant runoff voting shares the advantage of plurality voting of only requiring a single election, but shares the advantages of two-round runoffs in ensuring a majority winner and eliminating fear of "spoilers."

How IRV works. When voters go to the polls, they cast a vote for their favorite candidate, but also specify their runoff choice. Voters specify these choices by ranking preferred candidates in order of choice: first choice, second choice, third choice and so on. If a candidate wins a majority of first choices, that candidate has earned victory with majority support. But if no candidate has such strong support, the candidate with the fewest first choices is eliminated, and a second round of counting takes places. The votes of supporters of the eliminated candidate are not "wasted." Instead, their vote counts for their next favorite candidate as indicated on their ranked ballot, just as if they were voting for their second choice in a runoff. In each round of voting, a voter's ballot counts for whichever remaining candidate is ranked highest on the ballot. Eventually one candidate emerges as a majority winner.

Imagine that IRV had been used in the national tally of the 1992 presidential election, in which Bill Clinton won 43% of the vote, George Bush 38% and Ross Perot 19%. Since no candidate received an outright majority of first choices, the instant runoff would have taken place. The major candidate with the fewest votes, Perot, would have been eliminated, just as if he hadn’t qualified for the second round of a traditional two round runoff. In the next round of voting, supporters of Clinton and Bush would have been able to keep supporting their favorite candidate, but Perot supporters would have had their vote count for their runoff choice, either Bush or Clinton. This second round would have produced a majority winner for president in a single election.

Arguments for IRV: IRV is like holding a two-round runoff, but all with one vote. In addition to saving taxpayers millions of dollars in election costs, the instant runoff has several other important benefits:

• IRV promotes positive, issue-oriented campaigns and coalition-building because candidates know that winning may require being the runoff choice of their opponents' supporters.

• When replacing two-round runoff elections, IRV is effective campaign finance reform because candidates won't need to raise more money for a second election

• IRV removes the "spoiler effect" whereby minor party or independent candidates knock off major party candidates, increasing the choices available to the voters.

• IRV maximizes voter turnout because it encourages more candidacies (candidates don't have to be concerned about being tagged as "spoilers"), and voters don't have to return to the polls for special runoff elections.

• IRV all but eliminates the "lesser of two evils" problems, since voters can vote for their favorite candidate, knowing that if their first choice doesn't win, their vote will not be wasted.

While IRV can appear on paper to be a sensible solution to the problems of plurality voting or two-round run-offs, certain problems can arise. First, the system is simple for voters, but there is an initial education hurdle to explain the importance of ranking candidates. Second, voters accustomed to plurality elections might be disturbed if the candidate with the largest share of first choice votes was defeated in a later round of counting. Third, many older voting machines cannot be used for IRV, and upgrading vote-counting equipment to handle ranked ballots can be costly. Still, IRV is gathering more attention in the United States as a simple and cost-effective solution to the defects of plurality and two-round runoff elections.

Where IRV is used: IRV has been used for many years to elect Australia’s Lower House, the Republic of Ireland’s president, and a number of other official bodies. IRV is also used to elect the mayor of London and in 1998 was recommended by the Jenkins commission to elect the UK's House of Commons. In the United States, IRV has been seriously considered for a number of U.S. states and municipalities – most vigorously in Vermont, where the League of Women Voters and Common Cause have endorsed it for statewide elections, and in Alaska, where an initiative has qualified for the 2002 ballot to change state legislative and federal elections to IRV -- and it is used to elect the president of the American Political Science Association.

See also: IRV flow chart