What is "spoiler effect"

n. (context Voting theory English) the effect a minor party candidate with little chance of winning has upon a close election, when that candidate's presence in the election draws votes from a candidate similar to them, thereby causing a candidate dissimilar to them to win the election.

The spoiler effect is the effect of vote splitting between candidates or ballot questions with similar ideologies. One spoiler candidate's presence in the election draws votes from a major candidate with similar politics thereby causing a strong opponent of both or several to win. The minor candidate causing this effect is referred to as a spoiler. However, short of any electoral fraud, this presents no grounds for a legal challenge. The spoiler effect is a problem in plurality voting systems because they enable a candidate to win with less than half of the vote. The problem does not exist in preferential voting or ranked ballot voting systems because voters are allowed to rank their candidate choices, with their vote transferring to their second choice if their first choice does not win, and to their third choice if their second choice does not win, and so on.