Preferential voting is a method of voting in which each voter ranks candidates on a ballot. The rankings—usually expressed as the numbers 1, 2, 3, and so on—indicate the voter’s relative preference for each candidate in relation to the others.
Election systems vary in the ways that votes are recorded and counted. Most systems use the first-past-the-post, or plurality, method. Under this method, people vote for only one candidate, and the candidate who receives the most votes wins. But other election systems use variations of preferential voting. In these systems, voters rank multiple candidates, and specific algorithms (mathematical procedures) determine the winning candidate. There are a number of methods for the handling and counting of preferential votes.
The alternative vote method is used in Australian elections for the House of Representatives and for all Australian state elections except the Tasmanian lower house, the House of Assembly. Under this method, when electoral officers initially count the votes, they count only the first preference marked on each ballot. If one candidate receives more than half the total number of first preferences, he or she is elected. If not, the electoral officers eliminate the candidate with the fewest first preferences. They then take the ballots on which the eliminated candidate was ranked first and assign the votes to the remaining candidates according to the ballots’ second preferences. The process is repeated until one candidate has more than half the votes. This is sometimes called instant runoff voting or the Hare voting method, after the British lawyer Thomas Hare. Some American cities—including Portland, Maine; Oakland and San Francisco, California; and Minneapolis and St. Paul, Minnesota—use the same system. They call it ranked choice voting (RCV) or instant runoff voting.
The use of ranked choice voting in U.S. elections expanded in the early decades of the 2000’s. The states of Alaska and Maine, for example, use RCV for federal and state elections, including governor, senator, representative, and state legislature. Other states use RCV for primary and local elections, including for mayor. However, some jurisdictions that once used RCV have repealed its use and have reverted to plurality voting.
Some election systems have used variations of the alternative vote method. For instance, the American psychologist Clyde Coombs proposed a system in which the person who received the most last-place votes—rather than the person who received the fewest first preferences—would be eliminated.
Another widely used method for counting preferential votes is the simple majority runoff. Under this method, if no candidate wins a majority of first preferences, all candidates except the two front-runners are eliminated. Then, voters whose first preferences have been eliminated have their votes reassigned to their second preferences. A variation of this method is used to elect many mayors in the United States, as well as the president of France. Some variations involve holding a second election if there is no majority winner following a first election.
Mathematicians, political scientists, and election theorists have proposed a number of other methods for deciding elections with preferential voting. Some of these methods have actually been used. For example, the Borda count system—developed by Jean-Charles de Borda, a French mathematician—assigns each candidate a score depending on his or her ranking on each ballot. After all the ballots have been recorded, the total score determines the winner of the election. Variations of this method have been used in elections in Kiribati, Nauru, and elsewhere.
In Australian Senate elections, preferential votes are counted according to a system of proportional representation. Under this system, electoral officers determine the total number of valid ballots and then set a quota—that is, a minimum number of votes needed to gain election. A candidate who receives the quota is elected. Any additional votes the candidate receives above the quota are distributed to the remaining candidates according to the voters’ subsequent preferences. If all the vacancies are not filled after distribution, the candidate with the fewest votes is excluded and that candidate’s votes are distributed according to the preferences shown on the ballot paper, as in the alternative vote method. This process continues until sufficient candidates have been elected to fill all the vacancies. A reform introduced in 2016 allows for optional preferential voting. This means that voters do not need to rank all parties or candidates.
The Hare Clark system of proportional representation, used in elections for the Tasmanian House of Assembly, is a variation of the system used for Australian Senate elections. Andrew I. Clark, attorney general of Tasmania in the late 1800’s, introduced the system into the state.
