Editing Spoiler effect (section)

=== First-preference plurality ===
In cases where there are many similar candidates, spoiler effects occur most often in [[First-preference plurality|first-preference plurality (FPP)]].{{Citation needed|date=September 2024}} For example, in the United States, vote splitting is common in [[primary elections|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 [[First-preference plurality|FPP]] into a [[two-round system]].<ref name="Santucci">{{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 (US State)|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).'''"}}</ref><ref name="Gallagher">{{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}}</ref><ref name="Bowler">{{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}}</ref>

Vote splitting is the most common cause of spoiler effects in [[First-past-the-post voting|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.<ref name="King">{{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'.}}</ref><ref name="Sen-2017">{{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}}</ref> 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.<ref name="King" /><ref name="Buchler">{{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.}}</ref>