Spoiler effect

In decision theory, independence of irrelevant alternatives is a fundamental principle of rational choice which says that a decision between two outcomes, A or B, should not depend on the quality of a third, unrelated outcome C. A famous joke by Sidney Morgenbesser illustrates this principle:{{Cite journal |last=Pearce |first=David |date=March 2021 |title=Individual and social welfare: a Bayesian perspective |url=https://economia.uc.cl/wp-content/uploads/2022/12/Individual-and-Social-Welfare-A-Bayesian-Perspective-1-2.pdf |journal=Frisch Lecture Delivered to the World Congress of the Econometric Society}}

A man is deciding whether to order apple, blueberry, or cherry pie before settling on apple. The waitress informs him that the cherry pie is very good and a favorite of most customers. The man replies "in that case, I'll have the blueberry."

{{anchor|Strategic nomination|Manipulation}}

Voting systems that violate independence of irrelevant alternatives are susceptible to being manipulated by strategic nomination. Such systems may produce an incentive to entry, increasing a candidate's chances of winning if similar candidates join the race, or an incentive to exit, reducing the candidate's chances of winning.

Some systems are particularly infamous for their ease of manipulation, such as the Borda count, which exhibits a particularly severe entry incentive, letting 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,"{{Cite book |last=Black |first=Duncan |url=https://books.google.com/books?id=CRdnaPy8oB4C&q=honest&pg=PA182 |title=The Theory of Committees and Elections |date=1987 |publisher=Springer Science & Business Media |isbn=9780898381894 |language=en |orig-year=1958}}{{Cite book |last1=McLean |first1=Iain |url=https://books.google.com/books?id=0QPv9cg3g-sC&q=the%20voters%20found%20how%20to%20manipulate%20the%20Borda%20rule:%20not%20only%20by%20putting%20their%20most%20dangerous%20rival%20at%20the%20bottom%20of%20their%20lists,%20but%20also%20by%20truncating%20their%20lists&pg=PA40 |title=Classics of Social Choice |last2=Urken |first2=Arnold B. |last3=Hewitt |first3=Fiona |date=1995 |publisher=University of Michigan Press |isbn=978-0472104505 |language=en}} and eventually led to its abandonment by the French Academy of Sciences.

Other systems exhibit an exit incentive. The vote splitting effect in plurality voting demonstrates this method's strong exit incentive: if multiple candidates with similar views run in an election, their supporters' votes will be diluted, which may cause a unified opposition candidate to win despite having less support. This effect encourages groups of similar candidates to form an organization to make sure they don't step on each other's toes.{{cite journal | first=James|last=Green-Armytage | title=Strategic voting and nomination | journal=Social Choice and Welfare | publisher=Springer | volume=42 | issue=1 | year=2014 | issn=0176-1714 | jstor=43663746 | pages=111–138 | doi=10.1007/s00355-013-0725-3 | s2cid=253847024 | url=http://www.jstor.org/stable/43663746 | access-date=2024-02-23 | quote=... if two or more candidates with similar views run in the same plurality election, then the voters who support those views will be divided among them, giving an advantage to other candidates with opposed views. Therefore, it is helpful for groups of fairly like-minded people to form some kind of association – that is, a political party – which fields only one candidate per election, and which provides some kind of process for deciding whom this one candidate should be – that is, a primary.}}

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 majoritarian methods, and with a varying level of spoiler vulnerability with most rated voting methods.{{Notetag|Strategic voting can sometimes create additional spoiler-like behavior. However, this does not substantially affect the general order described here.}}

In cases where there are many similar candidates, spoiler effects occur most often in first-preference plurality (FPP).{{Citation needed|date=September 2024}} For example, in the United States, vote splitting is common in primaries, where many 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 running only one candidate. In a two-party system, party primaries effectively turn FPP into a two-round system.{{Cite web |last1=Santucci |first1=Jack |last2=Shugart |first2=Matthew |last3=Latner |first3=Michael S. |date=2023-10-16 |title=Toward a Different Kind of Party Government |url=https://protectdemocracy.org/work/toward-a-different-kind-of-party-government/ |url-status=live |archive-url=https://web.archive.org/web/20240716205506/https://protectdemocracy.org/work/toward-a-different-kind-of-party-government/ |archive-date=2024-07-16 |access-date=2024-07-16 |website=Protect Democracy |language=en-US |quote="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)."}}{{Cite book |last1=Gallagher |first1=Michael |title=The Politics of Electoral Systems |last2=Mitchell |first2=Paul |date=2005-09-15 |publisher=OUP Oxford |isbn=978-0-19-153151-4 |page=192 |language=en |chapter=The American Electoral System |quote="American elections become a two-round run-off system with a delay of several months between the rounds." |chapter-url=https://books.google.com/books?id=Igdj1P4vBwMC&q=%22American+elections+become+a+two-round+run-off+system+with+a+delay+of+several+months+between+the+rounds.%22&pg=PA3}}{{Citation |last1=Bowler |first1=Shaun |title=The United States: A Case of Duvergerian Equilibrium |date=2009 |work=Duverger's Law of Plurality Voting: The Logic of Party Competition in Canada, India, the United Kingdom and the United States |pages=135–146 |url=https://link.springer.com/chapter/10.1007/978-0-387-09720-6_9 |access-date=2024-08-31 |place=New York, NY |publisher=Springer |language=en |doi=10.1007/978-0-387-09720-6_9 |isbn=978-0-387-09720-6 |quote=In effect, the primary system means that the USA has a two-round runoff system of elections. |last2=Grofman |first2=Bernard |last3=Blais |first3=André|url-access=subscription }}

Vote splitting is the most common cause of spoiler effects in FPP. 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.{{Cite book |last1=King |first1=Bridgett A. |url=https://books.google.com/books?id=-bCJDAAAQBAJ |title=Why Don't Americans Vote? Causes and Consequences: Causes and Consequences |last2=Hale |first2=Kathleen |date=2016-07-11 |publisher=ABC-CLIO |isbn=9781440841163 |language=en |quote=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'.}}{{cite news |last1=Sen |first1=Amartya |last2=Maskin |first2=Eric |date=2017-06-08 |title=A Better Way to Choose Presidents |url=https://scholar.harvard.edu/files/maskin/files/the_new_york_review_of_books_-_a_better_way_to_choose_presidents_e._maskin_a._sen_.pdf |access-date=2019-07-20 |journal=New York Review of Books |language=en |issn=0028-7504 |quote=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}} 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.{{Cite book |last=Buchler |first=Justin |url=https://books.google.com/books?id=9bzmTImCLfgC |title=Hiring and Firing Public Officials: Rethinking the Purpose of Elections |date=2011-04-20 |publisher=Oxford University Press, USA |isbn=9780199759965 |language=en |quote=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.}}

Plurality-runoff methods like the two-round system and RCV still experience vote-splitting in each round. This produces a kind of spoiler effect called a center squeeze. Compared to plurality without primaries, the elimination of weak candidates in earlier rounds reduces their effect on the final results; however, spoiled elections remain common compared to other systems.{{Cite book |last=Borgers |first=Christoph |url=https://books.google.com/books?id=u_XMHD4shnQC |title=Mathematics of Social Choice: Voting, Compensation, and Division |date=2010-01-01 |publisher=SIAM |isbn=9780898716955 |language=en |quote=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}}{{Cite book |last=Poundstone |first=William |url=https://books.google.com/books?id=_24bJHyBV6sC |title=Gaming the Vote: Why Elections Aren't Fair (and What We Can Do About It) |date=2009-02-17 |publisher=Farrar, Straus and Giroux |isbn=9781429957649 |language=en |quote=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}} As a result, instant-runoff voting still tends towards two-party rule through the process known as Duverger's law.{{Cite web |last=Drutman |first=Lee |date=2024-09-12 |title=We need more (and better) parties |url=https://leedrutman.substack.com/p/we-need-more-and-better-parties |access-date=2024-09-19 |website=Undercurrent Events}} A notable example of this can be seen in Alaska's 2024 race, where party elites pressured candidate Nancy Dahlstrom into dropping out to avoid a repeat of the spoiled 2022 election.{{Cite book |last=Volić |first=Ismar |url=http://dx.doi.org/10.2307/jj.7492228 |title=Making Democracy Count |date=2024-04-02 |publisher=Princeton University Press |isbn=978-0-691-24882-0 |publication-date=2024-04-02 |at=Ch. 2 |chapter=Duverger's law |doi=10.2307/jj.7492228}}{{Cite news |last=Strassel |first=Kimberly A. |date=2024-08-27 |title=Ranked Choice May Die in Alaska |url=https://www.wsj.com/opinion/ranked-choice-may-die-in-alaska-4452235c |work=The Wall Street Journal}}{{Cite web |last=Early |first=Wesley |date=2024-09-05 |title=Why candidates are withdrawing from Alaska's general election |url=https://alaskapublic.org/2024/09/04/why-candidates-are-withdrawing-from-alaskas-general-election/ |access-date=2024-09-20 |website=Alaska Public Media |publisher=NPR |place=Anchorage, Alaska |language=en-US}}

Spoiler effects rarely occur when using tournament solutions, where candidates are compared 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. The resulting table of pairwise counts eliminates the step-by-step redistribution of votes, which is usually the cause for spoilers in other methods. 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.

Theoretical models suggest that somewhere between 90% and 99% of real-world elections have a Condorcet winner,{{Cite journal |last=Gehrlein |first=William V. |date=2002-03-01 |title=Condorcet's paradox and the likelihood of its occurrence: different perspectives on balanced preferences* |url=https://doi.org/10.1023/A:1015551010381 |journal=Theory and Decision |language=en |volume=52 |issue=2 |pages=171–199 |doi=10.1023/A:1015551010381 |issn=1573-7187|url-access=subscription }}{{Cite journal |last=Van Deemen |first=Adrian |date=2014-03-01 |title=On the empirical relevance of Condorcet's paradox |url=https://doi.org/10.1007/s11127-013-0133-3 |journal=Public Choice |language=en |volume=158 |issue=3 |pages=311–330 |doi=10.1007/s11127-013-0133-3 |issn=1573-7101|url-access=subscription }} and the first Condorcet cycle in a ranked American election was found in 2021.{{cite journal | last1=McCune | first1=David | last2=McCune | first2=Lori | title=The Curious Case of the 2021 Minneapolis Ward 2 City Council Election | journal=The College Mathematics Journal | date=2023-05-24 | issn=0746-8342 | doi=10.1080/07468342.2023.2212548 | pages=1–5 |arxiv=2111.09846 |quote=The 2021 Minneapolis election for city council seat in Ward 2 contained three candidates, each of whom has a legitimate claim to be the winner, the first known example of an American political election without a Condorcet winner ...}} Some systems like the Schulze method and ranked pairs have stronger spoiler resistance guarantees that limit which candidates can spoil an election without a Condorcet winner.{{cite arXiv | last=Schulze | first=Markus | title=The Schulze Method of Voting | eprint=1804.02973 | class=cs.GT| date=2018-03-15 |quote="The Smith criterion and Smith-IIA (where IIA means “independence of irrelevant alternatives”) say that weak alternatives should have no impact on the result of the elections ... the Schulze method, as defined in section 2.2, satisfies Smith-IIA."}}{{rp|228–229}}

Rated voting methods ask voters to assign each candidate a score on a scale (e.g. rating them from 0 to 10), instead of listing them from first to last. Highest median and score (highest mean) voting are the two most prominent examples of rated voting rules. Whenever voters rate candidates independently, the rating given to one candidate does not affect the ratings given to the other candidates. Any new candidate cannot change the winner of the race without becoming the winner themselves, which would disqualify them from the definition of a spoiler. For this to hold, in some elections, some voters must use less than their full voting power despite having meaningful preferences among viable candidates.

The outcome of rated voting depends on the scale used by the voter or assumed by the mechanism.{{cite journal | last=Roberts | first=Kevin W. S. | title=Interpersonal Comparability and Social Choice Theory | journal=The Review of Economic Studies | publisher=[Oxford University Press, Review of Economic Studies, Ltd.] | volume=47 | issue=2 | year=1980 | issn=0034-6527 | jstor=2297002 | pages=421–439 | doi=10.2307/2297002 | url=http://www.jstor.org/stable/2297002 | access-date=2024-09-25 |quote=If f satisfies U, I, P, and CNC then there exists a dictator.| url-access=subscription }} If the voters use relative scales, i.e. scales that depend on what candidates are running, then the outcome can change if candidates who don't win drop out.{{cite book | last=Arrow | first=Kenneth J. | title=Social Choice and Individual Values | publisher=Yale University Press | year=2012 | isbn=978-0-300-17931-6 | jstor=j.ctt1nqb90 | url=http://www.jstor.org/stable/j.ctt1nqb90 | access-date=2024-09-25 | pages=10–11 |quote=At best, it is contended that, for an individual, his utility function is uniquely determined up to a linear transformation ... the value of the aggregate (say a sum) are dependent on how the choice is made for each individual.}} Empirical results from panel data suggest that judgments are at least in part relative.{{cite journal | last1=Stadt | first1=Huib van de | last2=Kapteyn | first2=Arie | last3=Geer | first3=Sara van de | title=The Relativity of Utility: Evidence from Panel Data | journal=The Review of Economics and Statistics | publisher=The MIT Press | volume=67 | issue=2 | year=1985 | issn=0034-6535 | jstor=1924716 | pages=179–187 | doi=10.2307/1924716 | url=http://www.jstor.org/stable/1924716 | access-date=2024-04-28}}{{cite journal |last1=Richard H. |last2=Diener |first2=Ed |last3=Wedell |first3=Douglas H. |title=Intrapersonal and Social Comparison Determinants of Happiness: A Range-Frequency Analysis |journal=Journal of Personality and Social Psychology |date=1989 |volume=56 |issue=3 |pages=317–325 |doi=10.1037/0022-3514.56.3.317 |pmid=2926632 |url=https://psycnet.apa.org/record/1989-18931-001|url-access=subscription }} Thus, rated methods, as used in practice, may exhibit a spoiler effect caused by the interaction between the voters and the system, even if the system itself passes IIA given an absolute scale.

Spoiler effects can also occur in some methods of proportional representation, such as the single transferable vote (STV or RCV-PR) and the largest remainders method of party-list representation, where it is called a new party paradox. A new party entering an election causes some seats to shift from one unrelated party to another, even if the new party wins no seats. This kind of spoiler effect is avoided by divisor methods and proportional approval.{{Rp|Thm.8.3}}

{{See also|List of elections involving vote splitting|Protest vote|Single-issue politics}}

{{See also|Electoral fusion in the United States}}A spoiler campaign in the United States is often one that cannot realistically win but can still determine the outcome by pulling support from a more competitive candidate.{{Cite web |date=April 18, 2024 |title=The Spoiled Election: Independents and the 2024 Election |url=https://harvardpolitics.com/the-spoiled-election-independents-and-the-2024-election/ |access-date=2024-08-24 |website=Harvard Political Review |quote=Perot was running what is commonly referred to as a “spoiler campaign,” a campaign that cannot win the election but still impacts its outcome.}} The two major parties in the United States, the Republican Party and Democratic Party, have regularly won 98% of all state and federal seats.{{Cite journal |last=Masket |first=Seth |date=Fall 2023 |title=Giving Minor Parties a Chance |url=https://democracyjournal.org/magazine/70/giving-minor-parties-a-chance/ |journal=Democracy |volume=70}} The US presidential elections most consistently cited as having been spoiled by third-party candidates are 1844{{Cite book |last=Green |first=Donald J. |title=Third-party matters: politics, presidents, and third parties in American history |date=2010 |publisher=Praeger |isbn=978-0-313-36591-1 |location=Santa Barbara, Calif |pages=153–154}} and 2000.{{Cite journal |last=Burden |first=Barry C. |date=September 2005 |title=Ralph Nader's Campaign Strategy in the 2000 U.S. Presidential Election |url=http://dx.doi.org/10.1177/1532673x04272431 |journal=American Politics Research |volume=33 |issue=5 |pages=672–699 |doi=10.1177/1532673x04272431 |issn=1532-673X |s2cid=43919948|url-access=subscription }}{{Cite journal |last1=Herron |first1=Michael C. |last2=Lewis |first2=Jeffrey B. |date=April 24, 2006 |title=Did Ralph Nader spoil Al Gore's Presidential bid? A ballot-level study of Green and Reform Party voters in the 2000 Presidential election |journal=Quarterly Journal of Political Science |publisher=Now Publishing Inc. |volume=2 |issue=3 |pages=205–226 |doi=10.1561/100.00005039}} [https://wayback.archive-it.org/all/20080216081328/http://www.sscnet.ucla.edu/polisci/faculty/lewis/pdf/greenreform9.pdf Pdf.]{{cite news |last=Roberts |first=Joel |date=July 27, 2004 |title=Nader to crash Dems' party? |url=http://www.cbsnews.com/news/nader-to-crash-dems-party/ |work=CBS News}} The 2016 election is more disputed as to whether it contained spoiler candidates or not.{{Cite journal |last1=Devine |first1=Christopher J. |last2=Kopko |first2=Kyle C. |date=2021-09-01 |title=Did Gary Johnson and Jill Stein Cost Hillary Clinton the Presidency? A Counterfactual Analysis of Minor Party Voting in the 2016 US Presidential Election |url=https://www.degruyter.com/document/doi/10.1515/for-2021-0011/html?lang=en |journal=The Forum |language=en |volume=19 |issue=2 |pages=173–201 |doi=10.1515/for-2021-0011 |issn=1540-8884 |s2cid=237457376 |quote=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.|url-access=subscription }}{{Cite news |last1=Haberman |first1=Maggie |author-link=Maggie Haberman |last2=Hakim |first2=Danny |author-link2=Danny Hakim |last3=Corasaniti |first3=Nick |date=2020-09-22 |title=How Republicans Are Trying to Use the Green Party to Their Advantage |url=https://www.nytimes.com/2020/09/22/us/politics/green-party-republicans-hawkins.html?searchResultPosition=1 |access-date=2024-08-28 |work=The New York Times |language=en-US |issn=0362-4331 |quote=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.}}{{Cite web |last=Schreckinger |first=Ben |date=2017-06-20 |title=Jill Stein Isn't Sorry |url=https://www.politico.com/magazine/story/2017/06/20/jill-stein-green-party-no-regrets-2016-215281 |access-date=2023-06-07 |website=POLITICO Magazine |language=en}} For the 2024 presidential election, Republican lawyers and operatives have fought to keep right-leaning third-parties like the Constitution Party off swing state ballots{{Cite web |last=Levy |first=Marc |date=2024-08-21 |title=Democrats get a third-party hopeful knocked off Pennsylvania ballot, as Cornel West tries to get on |url=https://apnews.com/article/pennsylvania-ballot-2024-west-kennedy-cc5507101bcd198028b04945d2d03aa3 |access-date=2024-08-28 |website=AP News |language=en |quote=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.}} while working to get Cornel West on battleground ballots.{{Cite web |last=Slodysko |first=Brian |date=2024-07-16 |title=Kennedy and West third-party ballot drives are pushed by secretive groups and Republican donors |url=https://apnews.com/article/kennedy-west-third-party-2024-election-10c4c166ad4d41cab73660c33a69a58a |access-date=2024-08-25 |website=AP News |language=en |quote=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.}} Democrats have helped some right-leaning third-parties gain ballot access while challenging ballot access of left-leaning third-parties like the Green Party.{{Cite news |last=Schleifer |first=Theodore |date=2024-08-29 |title=To Beat Trump, Democrats Seek to Help Anti-Abortion Candidate |url=https://www.nytimes.com/2024/08/29/us/politics/trump-terry-anti-abortion.html |access-date=2024-08-30 |work=The New York Times |language=en-US |issn=0362-4331}} Barry Burden argues that they have almost no chance of winning the 2024 election but are often motivated by particular issues.{{Cite web |last=Burden |first=Barry C. |date=2024-04-30 |title=Third parties will affect the 2024 campaigns, but election laws written by Democrats and Republicans will prevent them from winning |url=https://theconversation.com/third-parties-will-affect-the-2024-campaigns-but-election-laws-written-by-democrats-and-republicans-will-prevent-them-from-winning-226877 |access-date=2024-08-28 |website=The Conversation |language=en-US}}

Third party candidates are always controversial because almost anyone could play spoiler.{{Cite web |last=Gift |first=Thomas |date=2024-01-11 |title=US election: third party candidates can tip the balance in a tight race – here's why Robert F Kennedy Jr matters |url=https://theconversation.com/us-election-third-party-candidates-can-tip-the-balance-in-a-tight-race-heres-why-robert-f-kennedy-jr-matters-220578 |access-date=2024-08-27 |website=The Conversation |language=en-US}}{{Cite news |last=Milligan |first=Susan |date=March 22, 2024 |title=The Promise and the Perils of the Third-Party Candidate |url=https://www.usnews.com/news/the-report/articles/2024-03-22/the-promise-and-the-perils-of-the-third-party-candidate |work=US News and World Report |quote=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.}} This is especially true in close elections where the chances of a spoiler effect increase.{{Cite web |last=Skelley |first=Geoffrey |date=2023-07-13 |title=Why A Third-Party Candidate Might Help Trump — And Spoil The Election For Biden |url=https://fivethirtyeight.com/features/third-party-candidate-spoiler-trump-biden/ |access-date=2024-08-28 |website=FiveThirtyEight |language=en-US}} 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.{{Cite web |last=Burden |first=Barry C. |author-link=Barry Burden |date=2024-04-30 |title=Third parties will affect the 2024 campaigns, but election laws written by Democrats and Republicans will prevent them from winning |url=https://theconversation.com/third-parties-will-affect-the-2024-campaigns-but-election-laws-written-by-democrats-and-republicans-will-prevent-them-from-winning-226877 |access-date=2024-08-28 |website=The Conversation |language=en-US}}{{Cite web |last=DeSilver |first=Drew |date=2024-06-27 |title=Third-party and independent candidates for president often fall short of early polling numbers |url=https://www.pewresearch.org/short-reads/2024/06/27/third-party-and-independent-candidates-for-president-often-fall-short-of-early-polling-numbers/ |access-date=2024-08-28 |website=Pew Research Center |language=en-US}} Third-party campaigns are more likely to result in the candidate a third party voter least wants in the White House. Third-party candidates prefer to focus on their platform than on their impact on the frontrunners.

An unintentional spoiler is one that has a realistic chance of winning but falls short and affects the outcome of the election. Some third-party candidates express ambivalence about which major party they prefer and their possible role as spoiler{{Cite news |last=Selk |first=Avi |date=2021-11-25 |title=Analysis {{!}} Green Party candidate says he might be part alien, doesn't care if he's a spoiler in Ohio election |url=https://www.washingtonpost.com/news/the-fix/wp/2018/08/09/green-party-candidate-says-he-might-be-part-alien-doesnt-care-if-he-spoils-ohio-election/ |access-date=2023-07-21 |newspaper=The Washington Post |language=en-US |issn=0190-8286}}{{Cite web |last1=Merica |first1=Dan |last2=Slodysko |first2=Brian |date=2024-08-19 |title=Republicans scrambled to get Cornel West on the Arizona ballot. The left-wing academic is OK with it |url=https://apnews.com/article/republican-lawyers-cornel-west-arizona-88cd1b4f698715a3071a93b5e1526074 |access-date=2024-08-27 |website=AP News |language=en}} or deny the possibility.{{cite web |author=Means |first=Marianne |date=February 4, 2001 |title=Opinion: Goodbye, Ralph |url=http://seattlepi.nwsource.com/opinion/means4.shtml |url-status=dead |archive-url=https://web.archive.org/web/20020526010840/http://seattlepi.nwsource.com/opinion/means4.shtml |archive-date=May 26, 2002 |website=Seattle Post-Intelligencer |df=mdy}}

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 most voters preferred Montroll to Kiss.{{Cite journal |last=Stensholt |first=Eivind |date=2015-10-07 |title=What Happened in Burlington? |url=https://ideas.repec.org//p/hhs/nhhfms/2015_026.html |journal=Discussion Papers |language=en |pages=13 |quote=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.}} The results of every possible one-on-one election can be completed as follows:

This leads to an overall preference ranking of:

1. Montroll – defeats all candidates below, including Kiss (4,064 to 3,476)
2. Kiss – defeats all candidates below, including Wright (4,313 to 4,061)
3. Wright – defeats all candidates below, including Smith (3,971 to 3,793)
4. Smith – defeats Simpson (5,570 to 721) and the write-in candidates

Montroll was therefore preferred over Kiss by 54% of voters, over Wright by 56%, and over Smith by 60%. Had Wright not run, Montroll would have won instead of Kiss.{{Cite web|url=https://www.electionscience.org/library/irv-and-core-support/|title=IRV and Core Support|website=The Center for Election Science|language=en-US|access-date=December 4, 2019}}

Because all ballots were fully released, it is possible to reconstruct the winners under other voting methods. While Wright would have won under plurality, Kiss won under IRV, and would have won under a two-round vote or a traditional nonpartisan blanket primary. Montroll, being the majority-preferred candidate, would have won if the ballots were counted using ranked pairs (or any other Condorcet method).{{Cite journal |last1=Graham-Squire |first1=Adam T. |last2=McCune |first2=David |date=2023-06-12 |title=An Examination of Ranked-Choice Voting in the United States, 2004–2022 |journal=Representation |volume=61 |language=en |pages=1–19 |doi=10.1080/00344893.2023.2221689|arxiv=2301.12075 }}

In Alaska's first-ever IRV election, Nick Begich was eliminated in the first round to advance Mary Peltola and Sarah Palin. However, the pairwise comparison shows that Begich was the Condorcet winner while Palin was both the Condorcet loser and a spoiler:

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In the wake of the election, a poll found 54% of Alaskans, including a third of Peltola voters, supported a repeal of RCV.{{cite web |last=Baruth |first=Philip |date=March 12, 2009 |title=Voting Paradoxes and Perverse Outcomes: Political Scientist Tony Gierzynski Lays Out A Case Against Instant Runoff Voting |url=http://vermontdailybriefing.com/?p=1213 |url-status=dead |archive-url=https://web.archive.org/web/20110726125814/http://vermontdailybriefing.com/?p=1213 |archive-date=July 26, 2011 |publisher=Vermont Daily Briefing}}{{cite web |last=Slota |first=Bianca |date=March 2, 2010 |title=Burlington voters repeal IRV |url=http://www.wcax.com/story/12074080/burlington-voters-repeal-irv |archive-url=https://web.archive.org/web/20160409132306/http://www.wcax.com/story/12074080/burlington-voters-repeal-irv |archive-date=April 9, 2016 |access-date=March 28, 2016 |publisher=Wcax.com}}{{cite web |last=Barlow |first=Daniel |date=April 27, 2010 |title=Instant run-off voting experiment ends in Burlington : Rutland Herald Online |url=http://www.rutlandherald.com/article/20100427/NEWS03/4270339/1004/NEWS03 |url-status=dead |archive-url=https://web.archive.org/web/20160304055602/http://www.rutlandherald.com/article/20100427/NEWS03/4270339/1004/NEWS03 |archive-date=March 4, 2016 |access-date=April 1, 2016 |website=Rutlandherald.com}} Observers noted such pathologies would have occurred under Alaska's previous primary system as well, leading several to suggest Alaska adopt any one of several alternatives without this behavior.{{Cite journal |last1=Felsenthal |first1=Dan S. |last2=Tideman |first2=Nicolaus |date=2014-01-01 |title=Interacting double monotonicity failure with direction of impact under five voting methods |url=https://www.sciencedirect.com/science/article/pii/S0165489613000723 |journal=Mathematical Social Sciences |volume=67 |pages=57–66 |doi=10.1016/j.mathsocsci.2013.08.001 |issn=0165-4896|url-access=subscription }}

• Comparison of electoral systems
• Independence of clones
• Independence of Smith-dominated alternatives
• Sortition

{{Reflist}}

• [https://www.npr.org/2024/09/22/nx-s1-5113108/third-party-voters "Third-party voters face a tough choice in a tight election"] (September 22, 2024) by NPR

Category:Electoral system criteria