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The spoiler effect is the effect of vote splitting between candidates or ballot questions[n 1] who often have 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.[1][2][3][4] The minor candidate causing this effect is referred to as a spoiler.[n 2] However, short of any electoral fraud, this presents no grounds for a legal challenge.

The spoiler effect is a problem in plurality voting systems because they enable a candidate to win with less than half of the vote.

The problem also exists in instant-runoff voting,[3][5][6][7][8][9] though it is reduced, because voters are allowed to rank their candidate choices, with their vote transferring to their second choice if their first choice does not win, and to their third choice if their second choice does not win, and so on. Other preferential voting or ranked ballot voting systems also suffer from variations of the spoiler effect, as they fail the independence of irrelevant alternatives (IIA) criterion (see §Mathematical definitions).

The problem does not exist in cardinal voting methods like approval voting, score voting, or majority judgment, since the rating of each candidate is independent of the ratings of other candidates.


Relationship with other effectsEdit

The spoiler candidate takes votes away from a more viable[n 3] 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 enable the candidate to determine deliberately which of the more viable candidates wins the election — a situation known as a kingmaker scenario. With a first-past-the-post voting 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.

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.[n 4] 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.[n 5]

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 definitionsEdit

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 electionsEdit

A 2014 analysis by Philip Bump for the Washington Post found that 1.5% of general election races in the U.S. from 2006 to 2012 were spoiled by third-party candidates.[10]

Presidential electionsEdit

Historically, the Democratic and Republican parties have benefited from the alleged spoiler effect created by the existing U.S. plurality voting system.[11][12] This benefit is based in the theory that not voting for other parties and for independents and that third parties and independent candidates themselves declining to run, means to avoid "wasting votes" or splitting the vote causing an election result not wanted.

These are third-party candidates who have been accused of denying victory to a major nominee in U.S. Presidential Elections; a notable case among these is the 1912 election, where Progressive Party candidate Theodore Roosevelt won almost 700,000 votes more than did the Republican incumbent, William Howard Taft,[13] and thus it could be said that Taft was the spoiler for Roosevelt in that election. This argument worried Republicans, who, after Woodrow Wilson won the 1912 election, became concerned that Roosevelt might return to split the Republican vote again.[14]

In 1968, George Wallace ran for president as the American Independent Party's nominee. He received numerous votes from Southern demographics that typically voted for Democratic candidates, thereby undercutting the candidacy of that election's Democratic nominee, Hubert Humphrey.[15]

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

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.[16] 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 argued 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. Thus, they 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.[17]

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.[18] Still, some observers began to refer to the spoiler effect as the "Nader effect" after the 2000 election.[19][20][21] A 2006 study found that at least 40% of Nader voters in Florida would have voted for Bush if Nader had not run, while the other 60% would have voted for Gore. The study concluded that this 60% "did indeed spoil the 2000 presidential election for Gore but only because of highly idiosyncratic circumstances, namely, Florida’s extreme closeness."[22]

Other US electionsEdit

Other countriesEdit

In the German presidential election of 1925, Communist Ernst Thälmann refused to withdraw his candidacy though it was extremely unlikely he would win the election and the leadership of the Communist International urged him not to run. In the second (and final) round of balloting, Thälmann won 1,931,151 votes or 6.4 percent. Centrist candidate Wilhelm Marx won 13,751,605 or 45.3 percent. And independent candidate Paul von Hindenburg, endorsed by the German nationalists, nationalist liberals, and Nazis, won 14,655,641 votes or 48.3 percent.[32] If most of Thälmann's supporters had voted for Marx instead of the right-wing nationalist Hindenburg, Marx would have won the election. The election of 1925 had great significance because in 1933 Hindenburg appointed Adolf Hitler as chancellor and then died the following year, giving Hitler unchecked control of the German government.[33] By contrast, Marx, who was dedicated to republican democracy, lived until 1946.

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 Robert 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 districts in which although the right and the far right had more than half of the votes, the left still won the election; they accuse the left of profiting from their split.

In Hong Kong it is a very common for the Pro-democracy camp, and it suffered greatly in many election including the 2016 Hong Kong legislative election and 2015 Hong Kong local elections. Usually for Pro-Democracy supporters, they have way different ideologies and suffer from factional disputes, which exacerbates after the advent of localist groups. Though have wider aggregate support, the seats earned is even less than the Pro-Beijing camp, like in Kowloon East, Pro-Democracy got over 55% ballots but eventually earn only 2 seats out of 5.

In Canada, in the 2004 federal election, the right-of-centre Conservative Party won power with 29.63% of the popular vote. Its two major competitors, the Liberal Party and the New Democratic Party (both left-of-centre), respectively garnered 36.73% and 15.68% of the vote. Similar vote splits between the two major left-of-centre parties continued to assist the Conservative Party in maintaining power in the 2006, 2008, and 2011 federal elections, despite a majority of the national popular vote going to left-of-centre parties in each race.

Also in Canada, in the province of Alberta's 2015 provincial election, the New Democratic Party (a left-of-centre party) won 62% of the seats with 40.6% of the provincial popular vote, following a division within the right-of-centre Progressive Conservative Party that left it with 27.8% of the vote, and its breakaway movement, the Wildrose Party, with 24.2% of the vote. In 2008, the last election in which the Progressive Conservative Party was unified, it garnered 52.72% of the provincial popular vote.


In sports, the "spoiler effect" refers to a similar phenomenon, in which a team or individual has been eliminated from the possibility of reaching the postseason, 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 alsoEdit

Notes and referencesEdit

  1. ^ Examples are the first past the post electoral system and in single transferable vote or similar systems with a first-preference votes winning percentage.
  2. ^ A term designed to appeal to a wider section of the public as a result of the widespread, often national support of political parties.
  3. ^ More viable by common public sentiment which may sometimes be indicated in opinion polls.
  4. ^ For example, if the Democrats had nominated both Hillary Clinton and Barack Obama for U.S. President in 2008, it would have allowed the Republican candidate (John McCain) to easily win; the voters who preferred both Clinton and Obama over McCain could not have been relied on to solve the strategy coordination problem on their own.
  5. ^ For example, in the United Kingdom, UKIP have a policy of not standing parliamentary candidates where the incumbent is a committed eurosceptic member of the large Conservative Party; however, one rebel spoiler candidate from the party, Jake Baynes, led to the defeat of David Heathcoat-Amory in Wells in the 2010 United Kingdom general election by the Liberal Democrats (UK).
  1. ^ Buchler, Justin (2011-04-20). Hiring and Firing Public Officials: Rethinking the Purpose of Elections. Oxford University Press, USA. ISBN 9780199759965. a spoiler effect occurs when entry by a third-party candidate causes party A to defeat party B even though Party B would have won in a two-candidate race.
  2. ^ King, Bridgett A.; Hale, Kathleen (2016-07-11). Why Don't Americans Vote? Causes and Consequences: Causes and Consequences. ABC-CLIO. ISBN 9781440841163. Those votes that are cast for minor party candidates are perceived as taking away pivotal votes from major party candidates. ... This phenomenon is known as the "spoiler effect'
  3. ^ a b Borgers, Christoph (2010-01-01). Mathematics of Social Choice: Voting, Compensation, and Division. SIAM. ISBN 9780898716955. Candidates C and D spoiled the election for B ... With them in the running, A won, whereas without them in the running, B would have won. ... Instant runoff voting ... does not do away with the spoiler problem entirely, although it ... makes it less likely
  4. ^ Heckelman, Jac C.; Miller, Nicholas R. (2015-12-18). Handbook of Social Choice and Voting. Edward Elgar Publishing. ISBN 9781783470730. A spoiler effect occurs when a single party or a candidate entering an election changes the outcome to favor a different candidate.
  5. ^ Poundstone, William (2009-02-17). Gaming the Vote: Why Elections Aren't Fair (and What We Can Do About It). Farrar, Straus and Giroux. ISBN 9781429957649. IRV is excellent for preventing classic spoilers-minor candidates who irrationally tip the election from one major candidate to another. It is not so good when the "spoiler" has a real chance of winning
  6. ^ "The Spoiler Effect". The Center for Election Science. 2015-05-20. Retrieved 2017-01-29.
  7. ^ "The Problem with Instant Runoff Voting |". Retrieved 2017-01-29. After a minor party is strong enough to win, on the other hand, a vote for them could have the same spoiler effect that it could have under the current plurality system
  8. ^ " - Example to demonstrate how IRV leads to "spoilers," 2-party domination". Retrieved 2017-01-29. IRV means betraying your true favorite third party candidate pays off. Voting third party can mean wasting your vote under IRV, just like under plurality.
  9. ^ The Center for Election Science (2013-12-02), Favorite Betrayal in Plurality and Instant Runoff Voting, retrieved 2017-01-29
  10. ^ Bump, Philip (8 October 2014). "How often do third-party candidates actually spoil elections? Almost never". The Fix. The Washington Post. Retrieved 17 May 2017.
  11. ^ "THE 1992 ELECTIONS: DISAPPOINTMENT -- NEWS ANALYSIS An Eccentric but No Joke; Perot's Strong Showing Raises Questions On What Might Have Been, and Might Be". The New York Times. November 5, 1992.
  12. ^
  13. ^ "United States presidential election of 1912". Encyclopedia Britannica. Retrieved 10 May 2017.
  14. ^ Nilsson, Jeff (5 May 2016). "100 Years Ago: Fear of a Republican Spoiler". Saturday Evening Post. Retrieved 10 May 2017.
  15. ^ Belsome, Ross; Newman, Robert J. (April 2007). "Ghosts of Elections Past: Third-Party Shepherds and Stray Voters" (PDF).
  16. ^ Public Disclosure Division (December 2001). "2000 Official Presidential General Election Results". Federal Election Commission. Retrieved August 30, 2010.
  17. ^ Rosenbaum, David E. (February 24, 2004). "Relax, Nader Advises Alarmed Democrats, but the 2000 Math Counsels Otherwise". The New York Times. New York. Retrieved August 30, 2010.
  18. ^ State Elections Offices. "2000 OFFICIAL PRESIDENTIAL GENERAL ELECTION RESULTS". Retrieved June 25, 2012.
  19. ^ Bacon Jr., Perry; Tumulty, Karen (May 31, 2004). "The Nader Effect". Time. Retrieved August 30, 2010.
  20. ^ Kuhn, David Paul (February 23, 2004). "The Nader Effect". CBS News. Retrieved August 30, 2010.
  21. ^ Cook, Charlie (March 9, 2004). "The Next Nader Effect". The New York Times. Retrieved August 30, 2010.
  22. ^ Herron, Michael; Lewis, Jeffrey (2006). "Did Ralph Nader Spoil a Gore Presidency? A Ballot-Level Study of Green and Reform Party Voters in the 2000 Presidential Election" (PDF) (published 2006-04-24).
  23. ^ Wilson, Chris; Ho, Alexander (3 November 2014). "The Surprisingly Low Impact of Libertarian Candidates". Time.
  24. ^ "Wisconsin GOP backs spoiler candidates in recall elections". WSJ.
  25. ^ Cutler, Eliot. "Who Stole Election Day?". The Wall Street Journal. The Wall Street Journal. Retrieved 26 January 2015.
  26. ^ Jacobs, Ben. "Could Maine Re-Elect Its Wingnut Governor Paul LePage?". The Daily Beast. The Daily Beast Company. Retrieved 26 January 2015.
  27. ^ Fallows, James. "Third-Party Watch in Maine". The Atlantic. The Atlantic Monthly Group. Retrieved 26 January 2015.
  28. ^ Nemitz, Bill. "Eliot Cutler facing up to 'spoiler' label". Portland Press Herald. MaineToday Media, Inc. Retrieved 26 January 2015.
  29. ^ Halkias, Telly. "Eliot Cutler and the Myth of Election Spoilers". Portland Daily Sun. Portland Daily Sun. Retrieved 26 January 2015.
  30. ^ Bycoffe, Aaron. "2013 Elections: Virginia Governor And More (LIVE RESULTS)". The Huffington Post. Retrieved 2015-06-07.
  31. ^ "Virginia Election Results 2014: Senate Map by County, Live Midterm Voting Updates". POLITICO. Retrieved 2015-06-07.
  32. ^ "Die Präsidenten des Deutschen Reiches 1919 – 1934". Retrieved 8 November 2018.
  33. ^ Carlson, Cody K. "This week in history: Hindenburg elected German president". Deseret News. Retrieved 8 November 2018.