Wasted vote effect

In electoral systems, a wasted vote is any vote which is not for an elected candidate or, more broadly, a vote that does not help to elect a candidate. The narrower meaning includes only those votes which are for a losing candidate or party. There is debate over whether votes that fall under this narrower definition are indeed wasted. A broader definition includes surplus votes for winning candidates who would have won anyway without the wasted vote.

Wasted votes are the basis of the efficiency gap measure of gerrymandering, where voters are grouped into electoral districts in such a way as to increase the wasted votes of one political faction and decrease the wasted votes of the other.

An electoral system which reduces the number of wasted votes can be considered desirable on grounds of fairness or on the more pragmatic basis that a voter who feels their vote has made no difference may feel detached from their government or lose confidence in the democratic process. The term "wasted vote" is especially used by advocates of systems like the single transferable vote, or instant-runoff voting which purport to reduce the numbers of such votes.

The term may be considered pejorative by opponents of such systems. Their arguments may either suggest that in any voting system each vote is wasted (unless the result is decided by a single vote), or that no vote is wasted as each one sends a political signal which will be taken into account in preparation for the subsequent election.

In election campaigns, a leading candidate may appeal to voters who support a less-popular candidate to vote instead for the leading candidate for tactical reasons, on the basis that a vote for their preferred candidate is likely to be wasted. In some electoral systems, it may be plausible for less-popular candidates to make similar appeals to supporters of more-popular candidates. In a plurality voting system, the term "wasted vote" is not usually applied to votes for the second-placed candidate, but rather to votes for candidates finishing third or lower. This is a reflection of Duverger's Law, i.e. the institutionalisation of a two-party system.

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