Spoiler effect
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In social choice theory and politics, the spoiler effect refers to a situation where a losing spoiler candidate affects the results of an election.[1] A voting system that is not affected by spoilers satisfies the condition independence of irrelevant alternatives.[2]
Arrow's impossibility theorem posits that all rank-based voting systems[note 1] are vulnerable to the spoiler effect. However, the frequency and severity of spoiler effects depends substantially on the voting method. Majority-rule methods are only rarely affected by spoilers, which are limited to rare[3][4] situations called cyclic ties.[5] Plurality is the most sensitive to spoilers, while ranked-choice voting (RCV-IRV) is still sensitive though less so in most scenarios.[6][7][8]
Spoiler effects exist but may be less common in some methods of proportional representation, such as the single transferable vote (STV-PR or RCV-PR) 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.
History
[edit]The Marquis de Condorcet studied the spoiler-dependency in voting methods back in the 1780s.[9]
Manipulation by politicians
[edit]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,"[10][11] and eventually led to its abandonment by the French Academy of Sciences.[11]
Vote-splitting systems like choose-one and instant-runoff (ranked choice) voting have the opposite problem: because running many similar candidates at once makes it difficult for any of them to win the election, these systems tend to concentrate power in the hands of parties and political machines, which serve the role of clearing the field and signalling a single candidate that voters should focus their support on; 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.[citation needed]
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
[edit]Different electoral systems have different levels of vulnerability to spoilers. As a rule of thumb, spoilers are extremely common with plurality voting, common in plurality-runoff methods, rare with paired counting (Condorcet), and impossible with rated voting.[note 2][citation needed]
| Electoral system | Spoiler effect |
|---|---|
| Plurality voting | High |
| Runoff/IRV/Ranked-choice | Medium |
| Proportional representation | Medium-low |
| Rated voting | Low |
| Deliberative democracy | Low |
| Tournament voting | Low |
Plurality-runoff methods like the two-round system[12] and instant-runoff voting[13] still suffer from vote-splitting in each round though they reduce the effect. As a result, they do not eliminate the spoiler effect. The elimination of weak spoilers in earlier rounds reduces their effects on the results compared to single-round plurality voting, but spoiled elections remain common, moreso than in other systems.[citation needed]
Modern tournament voting eliminates vote splitting effects completely, because every one-on-one matchup is evaluated independently.[12] If there is a Condorcet winner, Condorcet methods are completely invulnerable to spoilers; in practice, somewhere between 90% and 99% of real-world elections have a Condorcet winner.[14][15][better source needed] Some systems like ranked pairs have even stronger spoilerproofing guarantees that are applicable to most situations without a Condorcet winner.[citation needed]
Plurality voting
[edit]Vote splitting most easily occurs in plurality voting.[citation needed] In the United States vote splitting most commonly occurs in primary elections.[citation needed] The purpose of primary elections is to eliminate vote splitting among candidates in the same party before the general election. If primary elections or party nominations are not used to identify a single candidate from each party, the party that has more candidates is more likely to lose because of vote splitting among the candidates from the same party. In a two-party system, party primaries effectively turn plurality voting into a two-round system.
Vote splitting is the most common cause of spoiler effects in the commonly-used plurality vote and two-round runoff systems. 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.[16] 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.[16][17]
Runoff systems
[edit]Spoilers also occur in the two-round system and instant-runoff voting at a higher rate than for modern pairwise-counting or rated voting methods, though less often than in plurality.[18][19][8] A 2022 paper suggests that Instant-runoff voting does increase support for third-party candidates.[20][8]
Tournament (Condorcet) voting
[edit]Spoiler effects rarely occur when using tournament solutions, because each candidate's total in a paired comparison does not involve any other candidates. Instead, methods can separately compare every pair of candidates and check who would win in a one-on-one election.[21] This pairwise comparison means that spoilers can only occur in the rare situation[14][15] known as a Condorcet cycle.[21]
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 causes vote splitting in other methods.
Spoiler campaign
[edit]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.[22] The spoiler effect 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.
United States
[edit]The two major parties have regularly won 98% of all state and federal seats.[23] The US presidential elections most consistently cited as having been spoiled by third-party candidates are 1844[24] and 2000,[25][26][27][24] while 2016 impact is often discussed but more disputed as to whether it altered the outcome.[28][29][30] 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[31] while working to get Cornel West on battleground ballots.[32] Democrats have helped some right-leaning third-parties gain ballot access while challenging ballot access of left-leaning third-parties like the Green Party.[33]
Third party candidates are always controversial because almost anyone could play spoiler.[34][35] This is especially true in close elections where the chances of a spoiler effect increase.[36] 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.[37][38][23] Third-party campaigns are more likely to result in the candidate a third party voter least wants in the White House.[35] Third-party candidates prefer to focus on their platform than on their impact on the frontrunners.[35]
See also
[edit]Notes
[edit]- ^ In election science, ranked voting systems include plurality rule, which is equivalent to ranking all candidates and selecting the one with the most first-place votes.
- ^ Strategic voting can sometimes create the appearance of a spoiler for any method (including rated methods). However, this does not greatly affect the general ordering described here, except by making cardinal and Condorcet methods closer to even.
References
[edit]- ^ 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.
- ^ Miller, Nicholas R. (2019-04-01). "Reflections on Arrow's theorem and voting rules". Public Choice (journal). 179 (1): 113–124. doi:10.1007/s11127-018-0524-6. hdl:11603/20937. ISSN 1573-7101.
- ^ 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.
- ^ 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.
- ^ Holliday, Wesley H.; Pacuit, Eric (2023-02-11), Stable Voting, arXiv:2108.00542. "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."
- ^ 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. JSTOR 3088418.
In terms of the performance of the different election systems, we confirm the results of Merrill (1984, 1985, 1988) that in multicandidate elections run-off and sequential elimination systems perform far better than plurality elections, in that they are more likely to pick the Condorcet winner, and have a lower variance in their outcomes. This is true even if the distribution is skewed or bimodal. However, with skewed distributions, run-off and sequential elimination elections still have a bias away from the median in the direction of the mode, although this is typically smaller than that with plurality election.
- ^ 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
- ^ a b c "Explainer: Instant runoff voting". MIT Election Lab. April 25, 2023. Retrieved 2024-08-29.
- ^ 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.
- ^ Black, Duncan (1987) [1958]. The Theory of Committees and Elections. Springer Science & Business Media. ISBN 9780898381894.
- ^ a b McLean, Iain; Urken, Arnold B.; Hewitt, Fiona (1995). Classics of Social Choice. University of Michigan Press. ISBN 978-0472104505.
- ^ a b 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
- ^ 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
- ^ 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.
- ^ a b Van Deemen, Adrian (2014-03-01). "On the empirical relevance of Condorcet's paradox". Public Choice (journal). 158 (3): 311–330. doi:10.1007/s11127-013-0133-3. ISSN 1573-7101.
- ^ 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'.
- ^ 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.
- ^ 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
- ^ 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
- ^ Simmons, Alan James; Gutierrez, Manuel; Transue, John E. (May 2022). "Ranked-Choice Voting and the Potential for Improved Electoral Performance of Third-Party Candidates in America". American Politics Research. 50 (3): 366–378. doi:10.1177/1532673X211072388. ISSN 1532-673X.
- ^ a b Holliday, Wesley H.; Pacuit, Eric (2023-02-11), Stable Voting, arXiv:2108.00542. "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."
- ^ "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.
- ^ a b Masket, Seth (Fall 2023). "Giving Minor Parties a Chance". Democracy. 70.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Roberts, Joel (July 27, 2004). "Nader to crash Dems' party?". CBS News.
- ^ 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.
- ^ 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.
- ^ Schreckinger, Ben (2017-06-20). "Jill Stein Isn't Sorry". POLITICO Magazine. Retrieved 2023-06-07.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Skelley, Geoffrey (2023-07-13). "Why A Third-Party Candidate Might Help Trump — And Spoil The Election For Biden". FiveThirtyEight. Retrieved 2024-08-28.
- ^ 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.
- ^ 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.