Three-cornered-contest
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In a three-cornered-contest at an election, two candidates representing roughly the same viewpoint stand for election, thereby splitting the vote so that their common foe gets elected. This is an inevitable result of the first-past-the-post voting system where there are more than two candidates. The problem is also called the spoiler effect.
A partial but costly solution is to have a second round of voting, where only the top two votegetters are allowed to participate. But it costs considerable sums of money to run an election, and many voters can get exhausted, and do not participate in the second round. Voters who are overseas and vote by mail, such as members of the armed forces, may miss out because the mail cannot get there and back in the time available.
Another solution is to combine the first and second rounds into a single round of so-called instant-runoff voting, whereby the voter lists some or all of the candidates as reserve choices should their first choice drop out due to lack of support. IRV allows voters to express support for their true first choice, even if they are an unlikely winner, without wasting their vote, which still plays its full part in determining the decisive contest.
Another solution is to use a Condorcet method.
