Spoiler effect

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.

Relationship with other effects

The spoiler candidate takes votes away from a more viable candidate or candidates, a common effect called vote splitting. Where one opposing candidate is ideologically or politically similar and therefore receives far fewer votes than other opposing candidates to the spoiler candidate, then the vote splitting has a spoiler effect.

In some cases, even though the spoiler candidate cannot win themselves, their influences upon the voters may allow the candidate to determine deliberately which of the more viable candidates wins the election — a situation known as a kingmaker scenario. In the first past the post electoral system this is particularly feasible where a spoiler candidate recommends tactical voting or runs on a false manifesto to bolster the prospects of their secretly preferred winning candidate, which in some jurisdictions and circumstances can amount to electoral fraud.

In a preferential voting system, a voter can feel more inclined to vote for a minor party or independent as their first choice and they can record a preference between the remaining candidates, whether they are in a major or established party or not. For example, voters for a minor left-wing candidate might select a major left-wing candidate as their second choice, thus minimizing the probability that their vote will result in the election of a right-wing candidate, or voters for an independent candidate perceived as libertarian, or simply as the voter prefers that ideology might select a particular libertarian candidate as their second choice, thus minimising the probability of an authoritarian candidate being elected. Approval voting and proportional representation systems can also reduce the spoiler effect.

One of the main functions of political parties is to mitigate the effect of spoiler-prone voting methods by winnowing on a local level the contenders before the election. Each party nominates at most one candidate per office since each party expects to lose if they nominate more than one. In some cases, a party can expect to "lose" by "suffering a rival elected opponent" if they nominate more than zero, where two opponents exist and one is considered a candidate they can "work with" — a party may prefer the candidate who would win if the party nominates zero.

Thus, empirical observations of the frequency of spoiled elections do not provide a good measure of how prone to spoiling a particular voting method is, since the observations omit the relevant information about potential candidates who did not run because of not wanting to spoil the election.

Mathematical definitions

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

Arrow's impossibility theorem states 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 (also known as Plurality Rule). The independence of Smith-dominated alternatives (ISDA) criterion is much weaker than IIA; unlike IIA, some ranked-ballot voting methods can pass ISDA.

A possible definition of spoiling based on vote splitting is as follows: Let W denote the candidate who wins the election, and let X and S denote two other candidates. If X would have won had S not been one of the nominees, and if (most of) the voters who prefer S over W also prefer X over W (either S>X>W or X>S>W), then S is a spoiler. Here is an example to illustrate: Suppose the voters' orders of preference are as follows:

33%: S>X>W

15%: X>S>W

17%: X>W>S

35%: W>X>S

The voters who prefer S over W also prefer X over W. W is the winner under Plurality Rule, Top Two Runoff, and Instant Runoff. If S is deleted from the votes (so that the 33% who ranked S on top now rank X on top) then X would be the winner (by 65% landslide majority). Thus S is a spoiler with these three voting methods.

Spoiler effect in American elections

Presidential elections

Bush, Gore, and Nader (2000 U.S. presidential election)

The 2000 U.S. Presidential election is often cited as an example of the spoiler effect. In that election, Al Gore, the Democratic candidate, received more popular votes than George W. Bush, the Republican candidate, but lost in the electoral college. In the state of Florida, the final certified vote count showed Bush with just 537 more votes than Gore. Because Bush defeated Gore in Florida, he won the state, received more votes in the electoral college, and became president of the United States.

Gore supporters pointed out that, had candidate Ralph Nader, a liberal, not run in the election, the majority of the 97,421 votes he received in Florida would have been cast for Gore. Gore supporters contend that Nader's candidacy spoiled the election for Gore by taking away enough votes from Gore in Florida to swing the election to Bush. 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 Nader voters would have voted for Gore, 27 percent would have voted for Bush, and the rest would not have voted.

Nader himself and many of his supporters argued that most Nader voters would either have chosen another minor party candidate or abstained from voting, had Nader not been on the ballot. It should also be noted that all other third party candidates on the ballot in Florida received more than the 537 vote difference between Bush and Gore. Still, some observers began to refer to the spoiler effect as the "Nader effect" after the 2000 election.

Other alleged spoilers

These are third-party candidates who have been accused of denying victory to a major nominee in U.S. Presidential Elections:

Spoiler candidate	Election	"Denied victory" to	Winning candidate
James Birney	1844	Henry Clay	James Knox Polk
Martin van Buren	1848	Lewis Cass	Zachary Taylor
Peter Cooper	1876	Samuel J. Tilden	Rutherford B. Hayes
John St. John	1884	James G. Blaine	Grover Cleveland
James B. Weaver	1892	Benjamin Harrison	Grover Cleveland
William Howard Taft	1912	Theodore Roosevelt	Woodrow Wilson
George Wallace	1968	Hubert Humphrey	Richard Nixon
Ross Perot	1992	George H. W. Bush	Bill Clinton
Ralph Nader	2000	Al Gore	George W. Bush

Other elections

• In 1994, moderate Republican Marshall Coleman ran for the U.S. Senate as an independent, receiving over 11 percent of the vote in an election where Democrat Chuck Robb defeated Republican nominee Oliver North by only three percent of the vote.

• In 2010, Green Party candidate Bill Scheurer ran for Illinois 8th Congressional District against Democratic incumbent Melissa Bean. Republican Joe Walsh won the election in a surprising upset with only a 291 vote (0.1%) difference with Bean, while Scheurer received 6,494 votes (3.2%).

• As a result of the 2011 Wisconsin protests and subsequent recall elections, the Wisconsin Republican Party has encouraged spoiler candidates to run in the recall elections on the Democrat ticket in order to force the Democrats into a Primary election. Republicans argued that this will even the playing field in the recalls, as incumbents facing recall did not have the time to campaign due to their work load in the state senate.

• Maine politician Eliot Cutler, an independent, has been accused of siphoning enough votes from Democratic candidates to allow Republican Paul LePage to win the 2010 and 2014 gubernatorial elections with pluralities of the vote.

• Several races in the 2014 election cycle were allegedly influenced by spoiler candidates, most notably Hawaii's gubenatorial elections and the Kansas senatorial race. In the Mississippi senatorial Republican primary, a paper candidate drawing less than two percent of the vote prevented both top contenders, incumbent Thad Cochran and challenger Chris McDaniel, from avoiding a runoff; had the spoiler not run, McDaniel would have won the race, but Cochran won the subsequent runoff.
• In both the 2013 Virginia Gubernatorial Election and the 2014 Virginia US Senate Election, Libertarian Robert Sarvis received a number of votes greater than the difference between the Republican and Democratic candidates. . Given the similarity in Republican and Libertarian views, it is likely that the Republican would have won each election if not for the inclusion of Sarvis on the ballot.

Other countries

In New Zealand, there have been two notable cases of the spoiler effect. In the 1984 general election, the free-market New Zealand Party deliberately ran for office in order to weaken support for the incumbent Prime Minister Rob Muldoon. Later on, the 1993 general election saw the New Zealand Labour Party's vote split by The Alliance, which has been attributed to the vagaries of the first past the post electoral system. In response to these problems, New Zealand has since adopted the mixed-member proportional voting system.

Likewise, in France, the 2002 presidential elections have been cited as a case of the spoiler effect: the numerous left-wing candidates, such as Christiane Taubira and Jean-Pierre Chevènement, both from political parties allied to the French Socialist Party, or the three candidates from Trotskyist parties, which altogether totalled around 20%, have been charged with making Lionel Jospin, the P.S. candidate, lose the two-round election in the first round to the benefit of Jean-Marie Le Pen, who was separated from Jospin by only 0.68%. Some also cite the case of some circumscriptions where, although the right and the far-right were voted for by mote than the half of the voters, the left list still won the election, and accused the Socialist party of benefiting of this phenomenon.

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. For example, a baseball team that is ten games out of contention for a playoff berth could defeat a team that has a playoff berth several times. This could cause the would-be playoff team to be passed by in the rankings by the team directly behind it before the final positions at the end of the season are determined.

In individual participant sports, such as automobile racing, a racer with no hope of obtaining a championship title could prevent a racer with a chance at the title by defeating them, preventing the contending racer from earning critical points toward winning the title. Instead, the title would go to the contender directly behind him in the rankings, provided that second-tier racer is close enough to surpass and they win their own competition.

See also

• Strategic nomination
• Vote splitting

Notes and References

Notes

References