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Spoiler effect

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For the same effect in sports, see Elimination from postseason contention § Spoiler effect.
"Independence of spoilers" redirects here. For the logical property in decision theory, see Independence of irrelevant alternatives.
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In social choice theory and politics, the spoiler effect or refers to a situation where a losing candidate affects the results of an election simply by participating, assuming voter opinions don't change.[1][2] If a major candidate is perceived to have lost an election because of a minor candidate, the minor candidate is called a spoiler candidate and the major candidate is said to have been spoiled. Often times the term spoiler will be applied to candidates or situations which do not meet the full definition, typically in real-world scenarios where the introduction of a new candidate can cause voters to change their opinions, either through their campaign or merely by existing. If a voting system is not affected by spoilers under this definition, it satisfies the independence of irrelevant alternatives criterion.[3]

Arrow's impossibility theorem demonstrates that all rank-based voting systems are vulnerable to the spoiler effect. However, the frequency and severity of spoiler effects depends substantially on the voting method. Plurality is highly sensitive to spoilers while instant-runoff is less so, with both typically exhibiting this phenomenon through center-squeeze or vote splitting.[4][5] Majority-rule methods are only rarely affected by spoilers, which are limited to rare situations called cyclic ties.[6][7][8] Rated voting systems are not subject to Arrow's theorem, and many such systems are spoilerproof, so long as the defining assumption about voter opinions remains valid.[3][9][10]

Spoiler effects also occur in some methods of proportional representation, such as the single transferable vote and the largest remainders method of party-list representation. Here, a new party entering an election can cause seats to shift from one unrelated party to another, even if the new party wins no seats; this is known as the new states paradox.

Motivation

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In decision theory, independence of irrelevant alternatives is a fundamental principle of rationality, that says the choice between two outcomes, A or B, should not depend on an unrealized outcome, C. A famous joke by Sidney Morgenbesser illustrates this principle:

A man is deciding whether to order apple or blueberry pie before settling on apple. The waitress informs him that cherry pie is also an option, to which the man replies "in that case, I'll have the blueberry."

Amongst a long list of sometimes-conflicting voting criteria, activists and some social choice theorists have argued that voting methods should be spoiler-independent. While the concept in-and-of-itself is not controversial, strict mathematical satisfaction can be in direct conflict with other properties that are also considered valuable. The mathematician and political economist Marquis de Condorcet and politician Pierre Claude François Daunou studied and commented on the spoiler effect as early as the 1780s and 1800s, respectively.[11]

Manipulation by politicians

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Voting systems that violate independence of irrelevant alternatives are susceptible to being manipulated by strategic nomination. Some systems are particularly infamous for their ease of manipulation, such as the Borda count, which lets any party "clone their way to victory" by running a large number of candidates. This famously forced de Borda to concede that "my system is meant only for honest men,"[12][13] and eventually led to its abandonment by the French Academy of Sciences.[13]

Vote-splitting systems like choose-one and instant-runoff voting have the opposite problem: because running many similar candidates at once can make it difficult for any one of them to win the election, these systems tend to concentrate power in the hands of parties and political machines. The parties signal to the voters they should focus their support on a particular candidate. In many cases, this leads plurality voting systems to behave like a de facto two-round system, where the top-two candidates are nominated by party primaries.[14][15][16]

In some situations, a spoiler can extract concessions from other candidates by threatening to remain in the race unless they are bought off, typically with a promise of a high-ranking political position.[citation needed]

By electoral system

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Different electoral systems have different levels of vulnerability to spoilers. In general, spoilers are common with plurality voting, somewhat common in plurality-runoff methods, rare with condorcet methods, and mathematically impossible with cardinal methods. Strategic voting can sometimes create spoilers under the colloquial understanding, including in elections using rated methods, however, this does not greatly affect the general ordering described here.

Plurality voting

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Of all the voting methods, spoilers occur most often in plurality voting.[17][better source needed] In the United States, vote splitting commonly occurs in primary elections, where a large number of similar candidates run against each other. The purpose of a primary election is to eliminate vote splitting among candidates from the same party in the general election by agreeing to run a single individual. In a two-party system, party primaries effectively turn plurality voting into a two-round system.[14][15][16]

Vote splitting is the most common cause of spoiler effects in the plurality vote and two-round runoff systems.[18] In these systems, the presence of many ideologically similar candidates causes their vote total to be split between them, placing these candidates at a disadvantage.[19] This is most visible in elections where a minor candidate draws votes away from a major candidate with similar politics, thereby causing a strong opponent of both to win.[19][20]

Runoff systems

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Plurality-runoff methods like the two-round system and instant-runoff voting can still experience spoilers in each round, though their impact is reduced. The elimination of weak candidates in earlier rounds reduces their effects on the final results. Regardless, spoiled elections remain relatively common when compared to spoiler-proof or resistant systems.[10] [21][22] As a result, instant-runoff voting still tends towards two-party rule.[9]

In Burlington, Vermont's second IRV election, spoiler Kurt Wright knocked out Democrat Andy Montroll in the second round, leading to the election of Bob Kiss (despite the election results showing Montroll would have won a one-on-one election with Kiss).[23] In Alaska's first-ever IRV election, Nick Begich was defeated in the first round by spoiler candidate Sarah Palin.[24]

Tournament (Condorcet) voting

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Spoiler effects rarely occur when using tournament solutions, where candidates are paired in one-on-one matchups to determine relative preference. For each pair of candidates, there is a count for how many voters prefer the first candidate in the pair to the second candidate, and how many voters have the opposite preference. The resulting table of pairwise counts eliminates the step-by-step redistribution of votes, which is usually the cause for spoilers in other methods.[25] This pairwise comparison means that spoilers can only occur when there is a Condorcet cycle, where there is no single candidate preferred to all others.[26][27][25] In practice, somewhere between 90% and 99% of real-world elections have a Condorcet winner.[26][27]

Rated voting

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Rated voting methods ask voters to assign each candidate a score on a scale (usually from 0 to 10), instead of listing them from first to last. The best-known of these methods is score voting, which elects the candidate with the highest total number of points. Because voters rate candidates independently, changing one candidate's score does not affect those of other candidates, which is what allows rated methods to evade Arrow's theorem.

While true spoilers are not possible under score voting, voters who behave strategically in response to candidates can create pseudo-spoiler effects (which can be distinguished from true spoilers in that they are caused by voter behavior, rather than the voting system itself).

Spoiler campaign

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See also: List of elections involving vote splitting, Protest vote, and Single-issue politics

A spoiler campaign (or a spoiler candidate) is one that cannot realistically win but can still determine the outcome by splitting votes with a more competitive candidate.[28] A spoiler campaign is more prevalent in some systems than others, with the two-party systems (like the one in the United States) being relatively vulnerable to spoiler effects.

In some situations, a spoiler can extract concessions from other candidates by threatening to remain in the race unless they are bought off, typically with a promise of a high-ranking political position.[citation needed][original research?]

United States

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See also: Electoral fusion in the United States

The two major parties have regularly won 98% of all state and federal seats.[29] The US presidential elections most consistently cited as having been spoiled by third-party candidates are 1844[30] and 2000,[31][32][33][30] while 2016 impact is often discussed but more disputed as to whether it altered the outcome.[34][35][36] For the 2024 presidential election, Republican lawyers and operatives have fought to keep right-leaning third-parties like the Constitution Party off of swing state ballots[37] while working to get Cornel West on battleground ballots.[38] Democrats have helped some right-leaning third-parties gain ballot access while challenging ballot access of left-leaning third-parties like the Green Party.[39] According to the Associated Press, the GOP effort to prop up possible spoiler candidates in 2024 appears more far-reaching.[40]

Third party candidates are always controversial because almost anyone could play spoiler.[41][42] This is especially true in close elections where the chances of a spoiler effect increase.[43] Strategic voting, especially prevalent during high stakes elections with high political polarization, often leads to a third-party that underperforms its poll numbers with voters wanting to make sure their least favorite candidate is not in power.[44][45][29] Third-party campaigns are more likely to result in the candidate a third party voter least wants in the White House.[42] Third-party candidates prefer to focus on their platform than on their impact on the frontrunners.[42]

See also

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Notes

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References

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  1. ^ 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.
  2. ^ "The Spoiler Effect". The Center for Election Science. Retrieved 2024-03-03.
  3. ^ a b Miller, Nicholas R. (2019-04-01). "Reflections on Arrow's theorem and voting rules". Public Choice. 179 (1): 113–124. doi:10.1007/s11127-018-0524-6. hdl:11603/20937. ISSN 1573-7101.
  4. ^ McGann, Anthony J.; Koetzle, William; Grofman, Bernard (2002). "How an Ideologically Concentrated Minority Can Trump a Dispersed Majority: Nonmedian Voter Results for Plurality, Run-off, and Sequential Elimination Elections". American Journal of Political Science. 46 (1): 134–147. doi:10.2307/3088418. ISSN 0092-5853. As with simple plurality elections, it is apparent the outcome will be highly sensitive to the distribution of candidates.
  5. ^ 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
  6. ^ Gehrlein, William V. (2002-03-01). "Condorcet's paradox and the likelihood of its occurrence: different perspectives on balanced preferences*". Theory and Decision. 52 (2): 171–199. doi:10.1023/A:1015551010381. ISSN 1573-7187.
  7. ^ Van Deemen, Adrian (2014-03-01). "On the empirical relevance of Condorcet's paradox". Public Choice. 158 (3): 311–330. doi:10.1007/s11127-013-0133-3. ISSN 1573-7101.
  8. ^ Holliday, Wesley H.; Pacuit, Eric (2023-02-11), Stable Voting, arXiv:2108.00542, retrieved 2024-03-11. "This is a kind of stability property of Condorcet winners: you cannot dislodge a Condorcet winner A by adding a new candidate B to the election if A beats B in a head-to-head majority vote. For example, although the 2000 U.S. Presidential Election in Florida did not use ranked ballots, it is plausible (see Magee 2003) that Al Gore (A) would have won without Ralph Nader (B) in the election, and Gore would have beaten Nader head-to-head. Thus, Gore should still have won with Nader included in the election."
  9. ^ a b Poundstone, William. (2013). Gaming the vote : why elections aren't fair (and what we can do about it). Farrar, Straus and Giroux. pp. 168, 197, 234. ISBN 9781429957649. OCLC 872601019. IRV is subject to something called the "center squeeze." A popular moderate can receive relatively few first-place votes through no fault of her own but because of vote splitting from candidates to the right and left. ... Approval voting thus appears to solve the problem of vote splitting simply and elegantly. ... Range voting solves the problems of spoilers and vote splitting
  10. ^ a b "The Spoiler Effect". The Center for Election Science. 2015-05-20. Retrieved 2017-01-29.
  11. ^ McLean, Iain (1995-10-01). "Independence of irrelevant alternatives before Arrow". Mathematical Social Sciences. 30 (2): 107–126. doi:10.1016/0165-4896(95)00784-J. ISSN 0165-4896.
  12. ^ Black, Duncan (1987) [1958]. The Theory of Committees and Elections. Springer Science & Business Media. ISBN 9780898381894.
  13. ^ a b McLean, Iain; Urken, Arnold B.; Hewitt, Fiona (1995). Classics of Social Choice. University of Michigan Press. ISBN 978-0472104505.
  14. ^ a b Santucci, Jack; Shugart, Matthew; Latner, Michael S. (2023-10-16). "Toward a Different Kind of Party Government". Protect Democracy. Archived from the original on 2024-07-16. Retrieved 2024-07-16. Finally, we should not discount the role of primaries. When we look at the range of countries with first-past-the-post (FPTP) elections (given no primaries), none with an assembly larger than Jamaica's (63) has a strict two-party system. These countries include the United Kingdom and Canada (where multiparty competition is in fact nationwide). Whether the U.S. should be called 'FPTP' itself is dubious, and not only because some states (e.g. Georgia) hold runoffs or use the alternative vote (e.g. Maine). Rather, the U.S. has an unusual two-round system in which the first round winnows the field. This usually is at the intraparty level, although sometimes it is without regard to party (e.g. in Alaska and California).
  15. ^ a b Gallagher, Michael; Mitchell, Paul (2005-09-15). "The American Electoral System". The Politics of Electoral Systems. OUP Oxford. p. 192. ISBN 978-0-19-153151-4. American elections become a two-round run-off system with a delay of several months between the rounds.
  16. ^ a b Bowler, Shaun; Grofman, Bernard; Blais, André (2009), "The United States: A Case of Duvergerian Equilibrium", Duverger's Law of Plurality Voting: The Logic of Party Competition in Canada, India, the United Kingdom and the United States, New York, NY: Springer, pp. 135–146, doi:10.1007/978-0-387-09720-6_9, ISBN 978-0-387-09720-6, retrieved 2024-08-31, In effect, the primary system means that the USA has a two-round runoff system of elections.
  17. ^ "Top 5 Ways Plurality Voting Fails". The Center for Election Science. 2015-03-30. Retrieved 2017-10-07. You likely have opinions about all those candidates. And yet, you only get a say about one.
  18. ^ Sen, Amartya; Maskin, Eric (2017-06-08). "A Better Way to Choose Presidents" (PDF). New York Review of Books. ISSN 0028-7504. Retrieved 2019-07-20. plurality-rule voting is seriously vulnerable to vote-splitting ... runoff voting ... as French history shows, it too is highly subject to vote-splitting. ... [Condorcet] majority rule avoids such vote-splitting debacles because it allows voters to rank the candidates and candidates are compared pairwise
  19. ^ a b 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'.
  20. ^ 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.
  21. ^ 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
  22. ^ 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 tip the election from one major candidate to another. It is not so good when the 'spoiler' has a real chance of winning
  23. ^ Stensholt, Eivind (2015-10-07). "What Happened in Burlington?". Discussion Papers: 13. There is a Condorcet ranking according to distance from the center, but Condorcet winner M, the most central candidate, was squeezed between the two others, got the smallest primary support, and was eliminated.
  24. ^ Clelland, Jeanne N. (2023-02-28), Ranked Choice Voting And the Center Squeeze in the Alaska 2022 Special Election: How Might Other Voting Methods Compare?, arXiv:2303.00108
  25. ^ a b Holliday, Wesley H.; Pacuit, Eric (2023-02-11), Stable Voting, arXiv:2108.00542, retrieved 2024-03-11. "This is a kind of stability property of Condorcet winners: you cannot dislodge a Condorcet winner A by adding a new candidate B to the election if A beats B in a head-to-head majority vote. For example, although the 2000 U.S. Presidential Election in Florida did not use ranked ballots, it is plausible (see Magee 2003) that Al Gore (A) would have won without Ralph Nader (B) in the election, and Gore would have beaten Nader head-to-head. Thus, Gore should still have won with Nader included in the election."
  26. ^ a b Gehrlein, William V. (2002-03-01). "Condorcet's paradox and the likelihood of its occurrence: different perspectives on balanced preferences*". Theory and Decision. 52 (2): 171–199. doi:10.1023/A:1015551010381. ISSN 1573-7187.
  27. ^ a b Van Deemen, Adrian (2014-03-01). "On the empirical relevance of Condorcet's paradox". Public Choice. 158 (3): 311–330. doi:10.1007/s11127-013-0133-3. ISSN 1573-7101.
  28. ^ "The Spoiled Election: Independents and the 2024 Election". Harvard Political Review. April 18, 2024. Retrieved 2024-08-24. Perot was running what is commonly referred to as a "spoiler campaign," a campaign that cannot win the election but still impacts its outcome.
  29. ^ a b Masket, Seth (Fall 2023). "Giving Minor Parties a Chance". Democracy. 70.
  30. ^ a b Green, Donald J. (2010). Third-party matters: politics, presidents, and third parties in American history. Santa Barbara, Calif: Praeger. pp. 153–154. ISBN 978-0-313-36591-1.
  31. ^ Burden, Barry C. (September 2005). "Ralph Nader's Campaign Strategy in the 2000 U.S. Presidential Election". American Politics Research. 33 (5): 672–699. doi:10.1177/1532673x04272431. ISSN 1532-673X. S2CID 43919948.
  32. ^ Herron, Michael C.; Lewis, Jeffrey B. (April 24, 2006). "Did Ralph Nader spoil Al Gore's Presidential bid? A ballot-level study of Green and Reform Party voters in the 2000 Presidential election". Quarterly Journal of Political Science. 2 (3). Now Publishing Inc.: 205–226. doi:10.1561/100.00005039. Pdf.
  33. ^ Roberts, Joel (July 27, 2004). "Nader to crash Dems' party?". CBS News.
  34. ^ Devine, Christopher J.; Kopko, Kyle C. (2021-09-01). "Did Gary Johnson and Jill Stein Cost Hillary Clinton the Presidency? A Counterfactual Analysis of Minor Party Voting in the 2016 US Presidential Election". The Forum. 19 (2): 173–201. doi:10.1515/for-2021-0011. ISSN 1540-8884. S2CID 237457376. The perception that Johnson and Stein 'stole' the 2016 presidential election from Clinton is widespread...Our analysis indicates that Johnson and Stein did not deprive Clinton of an Electoral College majority, nor Trump the legitimacy of winning the national popular vote.
  35. ^ Haberman, Maggie; Hakim, Danny; Corasaniti, Nick (2020-09-22). "How Republicans Are Trying to Use the Green Party to Their Advantage". The New York Times. ISSN 0362-4331. Retrieved 2024-08-28. Four years ago, the Green Party candidate played a significant role in several crucial battleground states, drawing a vote total in three of them — Wisconsin, Michigan and Pennsylvania — that exceeded the margin between Donald J. Trump and Hillary Clinton.
  36. ^ Schreckinger, Ben (2017-06-20). "Jill Stein Isn't Sorry". POLITICO Magazine. Retrieved 2023-06-07.
  37. ^ Levy, Marc (2024-08-21). "Democrats get a third-party hopeful knocked off Pennsylvania ballot, as Cornel West tries to get on". AP News. Retrieved 2024-08-28. Republicans and Democrats view third-party candidates as a threat to siphon critical support from their nominees, especially considering that Pennsylvania was decided by margins of tens of thousands of votes both in 2020 for Democrat Joe Biden and in 2016 for Trump.
  38. ^ Slodysko, Brian (2024-07-16). "Kennedy and West third-party ballot drives are pushed by secretive groups and Republican donors". AP News. Retrieved 2024-08-25. there are signs across the country that groups are trying to affect the outcome by using deceptive means — and in most cases in ways that would benefit Republican Donald Trump. Their aim is to whittle away President Joe Biden's standing with the Democratic Party's base by offering left-leaning, third-party alternatives who could siphon off a few thousand protest votes in close swing state contests...Legal experts say elections will continue to be susceptible to dirty tricks and chicanery unless the more states adopt different methods of casting a ballot, like ranked choice voting, which allows voters to weight their candidate preferences.
  39. ^ Schleifer, Theodore (2024-08-29). "To Beat Trump, Democrats Seek to Help Anti-Abortion Candidate". The New York Times. ISSN 0362-4331. Retrieved 2024-08-30.
  40. ^ Slodysko, Brian; Merica, Dan (2024-09-01). "GOP network props up liberal third-party candidates in key states, hoping to siphon off Harris votes". AP News. Retrieved 2024-09-06.
  41. ^ Gift, Thomas (2024-01-11). "US election: third party candidates can tip the balance in a tight race – here's why Robert F Kennedy Jr matters". The Conversation. Retrieved 2024-08-27.
  42. ^ a b c Milligan, Susan (March 22, 2024). "The Promise and the Perils of the Third-Party Candidate". US News and World Report. And despite the contenders' claims that the nation deserves an alternative to two unpopular major party choices, the reality, experts say, is that these back-of-the-pack candidates may well cement the election of the candidate they least want in the White House.
  43. ^ Skelley, Geoffrey (2023-07-13). "Why A Third-Party Candidate Might Help Trump — And Spoil The Election For Biden". FiveThirtyEight. Retrieved 2024-08-28.
  44. ^ Burden, Barry C. (2024-04-30). "Third parties will affect the 2024 campaigns, but election laws written by Democrats and Republicans will prevent them from winning". The Conversation. Retrieved 2024-08-28.
  45. ^ DeSilver, Drew (2024-06-27). "Third-party and independent candidates for president often fall short of early polling numbers". Pew Research Center. Retrieved 2024-08-28.
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