Spoiler effect

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The "spoiler effect" is a term to describe the effect a minor party candidate with little chance of winning can have on a close election, in which their candidacy results in the election being won by a candidate dissimilar to them rather than a candidate similar to them. The minor candidate is often referred to as a "spoiler."

If preferential ballots are not used, the spoiler candidate takes votes away from the viable similar candidate through vote splitting. If the spoiler candidate can determine which viable candidate wins, the situation also is a kingmaker scenario.

The "spoiler effect" is one of the components contributing to the effect known as Duverger's law, which states that the first-past-the-post election system creates and preserves a two-party system.

Preferential voting systems can eliminate the spoiler effect. In a preferential voting system, a voter can vote for a minor party candidate as their first choice, and in addition, they can record a preference between the remaining candidates, whether they are in a "major party" or not. For example, voters for a very liberal candidate might select a somewhat liberal candidate as their second choice, thus minimizing the chances that their vote will result in the election of a conservative candidate. Approval voting can also reduce the impact of the "spoiler effect".

[edit] Mathematical definitions

Possible mathematical definitions for the spoiler effect include failure of independence of irrelevant alternatives (IIA) and vote splitting.

Arrow's impossibility theorem shows that rank-voting systems are unable to satisfy the independence of irrelevant alternatives criterion without exhibiting other undesirable properties as a consequence. However, different voting systems are affected to a greater or lesser extent by IIA failure. For example, instant runoff voting is considered to have less frequent IIA failure than First Past the Post. The independence of Smith-dominated alternatives criterion is similar to IIA, but which can be passed by some ranked ballot methods.

[edit] The spoiler effect in American presidential elections

One often cited example of the "spoiler effect" at work was the 2000 U.S. Presidential election. In that election, George W. Bush and Al Gore had a very close election in many states, with neither candidate winning a majority of the votes. In the state of Florida, the final certified vote totals show that Bush won just 537 more votes than Gore, thus winning the state. Some Gore supporters believed that many of the 97,421 votes that went to Ralph Nader in that state would likely have been votes for Gore, had Nader not been running in the election. Some Gore supporters contend that Nader's candidacy "spoiled" the election for Gore by "taking away" enough votes from Gore in Florida and many other states (in particular, New Hampshire being the allegation most statistically supportable) to allow Bush to win. Their argument is bolstered by a poll of Nader voters, asking them for whom they would have voted had Nader not run, which said 45 percent of them would have voted for Gore, 27 percent would have voted for Bush, and the rest would not have voted^[1]. Nader supporters say he was running, in part, to protest the positions of Bush and Gore. Ralph Nader, defending himself claimed "Defeat is a powerful motivator that democracy allows and encourages. Had Nader not been on the ballot, pro-Bush or anti-Gore voters might have voted for Bush". Nader himself and many of his supporters argue that most Nader voters would have chosen another minor party candidate, or abstained from voting, had he not been on the ballot. Some observers began to refer to this as the "Nader effect" after the 2000 election. Other observers note that this phenomenon existed long before Nader.

These are third-party candidates who have been accused of denying victory to a major nominee.

The spoiler effect also sometimes occurs in congressional elections and elections for state offices. For example, in 1994 moderate Republican Marshall Coleman ran for the U.S. Senate as an independent, receiving over 11% of the vote in an election which Democrat Chuck Robb defeated controversial Republican nominee Oliver North by only 3%.

The spoiler effect has also been seen in other countries, such as Trinidad and Tobago, in which a minority party with no chance of winning, The Congress of the People, took votes from its former party, The United National Congress, causing this party to lose seats and thus allowing the incumbent People's National Movement, highly disfavoured for the elections, to take the Government role again.

[edit] Sports

In sports, the "spoiler effect" refers to a similar phenomenon, in which a team or individual has failed to win enough games or competitions to make the playoffs or qualification rounds like the finals, but affects the playoffs or finals anyway by beating a more successful team or individual before the end of the season. One example is a baseball team that is 10 games out of contention for a playoff berth but could defeat numerous times a team that has a playoff berth. This could cause that would be playoff team to be passed by in the rankings by the team(s) directly behind it before the final positions at the end of the season are determined. In individual participant sports such as bicycle racing a racer with no hope of obtaining an championship title could prevent a racer with a chance at the title by defeating him/her, preventing the contending racer from earning critical points toward winning the title, giving it to a contender directly behind him in the rankings, provided that second-tier racer is close enough to surpass and he/she wins her own competitions.