Page "Two-round system" Paragraph 56

Runoff voting can be influenced by strategic nomination ; this is where 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 a candidate who knows they are unlikely to win can ensure that another candidate they support 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 its supporters.

A famous example of this spoiler effect occurred in the 2002 French presidential election, when so many left-wing candidates stood in the first round that all of them were eliminated and two right-wing candidates advanced to the second round.

Conversely, an important faction may have an interest in helping fund the campaign of smaller factions with a very different political agenda, so that these smaller parties end up weakening their own agenda.