Tactical Manipulation of Runoff Voting - Strategic Nomination

Strategic Nomination

Runoff voting can be influenced by strategic nomination; candidates and political factions influence the result of an election by either nominating extra candidates or withdrawing a candidate who would otherwise have stood. Runoff voting is vulnerable to strategic nomination for the same reasons that it is open to the voting tactic of compromising. This is because it is sometimes necessary for a candidate who knows they are unlikely to win to ensure that another candidate he supports makes it to the second round by withdrawing from the race before the first round occurs, or by never choosing to stand in the first place. By withdrawing candidates a political faction can avoid the spoiler effect, whereby a candidate splits the vote of her supporters and prevents any candidate acceptable to them from surviving to the last round.

Runoff votings system of two rounds makes it less vulnerable to the spoiler effect than the plurality system. This is because a potential spoiler candidate often has only minor support so that candidate will not take away sufficient support from any candidate likely to win in the second round to prevent the other candidate from surviving to that point. Voters can counteract the effect of vote splitting in the first round, in the two-round system, by using the compromise tactic. The spoiler effect is impossible in the second round because there are only two candidates.

Because it is vulnerable to certain forms of strategic nomination IRV is said by electoral scientists to fail the, independence of irrelevant alternatives criterion. This criterion is so strict that it is failed by almost all voting systems, even those that are less susceptible to strategic nomination than runoff voting.