First Past the Post electoral system: Difference between revisions
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== Notes ==
FPTP can be done either with a [[choose-one ballot]], or with a [[ranked ballot]] (by only looking at a voter's 1st choice candidate; if the voter has several first choices, it is recommended to split their vote equally between each of those candidates, similar to [[cumulative voting]]), or with a [[rated ballot]] (by identifying the candidates given the highest rating on the ballot as the voter's 1st choice(s)).
FPTP is notable among voting methods for offering a voter no way to express a preference for more than one candidate; see the [[ballot]] article for examples of other ballot types. It passes [[monotonicity]], meaning that a candidate can never be hurt if voters vote for that candidate, which is a notable property. In terms of voter behavior, it has been widely observed that FPTP tends to result in elections with two sharply opposed major candidates. [[Duverger's law]] and the [[center squeeze effect]] offer insight into this; essentially, voters are encouraged to group up to ensure their candidate can get the most votes, yet this prevents some voters from supporting their favorite candidate. [[Runoff voting]] and [[Instant runoff voting]] are two voting methods highly based on FPTP-like principles. ▼
▲FPTP is notable among voting methods for offering a voter no way to express a preference for more than one candidate; see the [[ballot]] article for examples of other ballot types. It passes [[monotonicity]], meaning that a candidate can never be hurt if voters vote for that candidate, which is a notable property. In terms of voter behavior, it has been widely observed that FPTP tends to result in elections with at most two sharply opposed major candidates. [[Duverger's law]] and the [[center squeeze effect]] offer insight into this; essentially, voters are encouraged to group up to ensure their candidate can get the most votes, yet this prevents some voters from supporting their favorite candidate. [[Runoff voting]] and [[Instant runoff voting]] are two voting methods highly based on FPTP-like principles; see [[:Category:FPTP-based voting methods|Category:FPTP-based voting methods]].
In the single-winner context, Approval is almost a [[Pareto criterion|Pareto]] improvement (pun) over FPTP; it preserves its simplicity and good qualities while adding in others, such as passing [[Favorite Betrayal]]. In the multiwinner context, [[SNTV]] is more proportional than [[Bloc vote|Bloc Approval voting]], so a [[Cardinal PR]] method using Approval ballots may work better.
FPTP can be extended to the multi-winner case either as [[SNTV]] or [[Plurality-at-large voting]]. An in-between form is limited voting, which gives a voter the ability to choose fewer candidates than the number of seats to be filled, but usually lets voters pick more than one candidate. The general principle in any multi-winner extension of FPTP is that a voter can support at most as many candidates as there are seats to be filled.
One of the biggest complaints against FPTP is that it has a [[spoiler effect]]. This is most easily visualized by observing that FPTP passes the [[majority criterion]] but not the [[mutual majority criterion]]:
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C has the most 1st choices and wins here with 49 votes. Yet if one of A or B drops out, then the remaining candidate of the two will be a [[majority]]'s 1st choice and thus win with 51 votes. [[IRV]]/[[RCV]] guarantees such scenarios don't occur, with [[Smith-efficient]][[Condorcet methods]] giving an even stronger guarantee: if C's voters had a preference between A or B, they'd have the power to ensure their preference between the majority's candidates wins. This is also an example of FPTP failing the [[Majority loser criterion|majority loser criterion]].
FPTP can be done by allowing each voter to cross out the names of all of the candidates they don't support. In this formulation, a voter must cross out all but one candidate's name or have their ballot thrown out. [[Approval voting]] is where a voter may cross out only as many names as they desire.
[[Cumulative voting]] is an extension of FPTP in the sense that it also restricts a voter to putting their maximal vote weight or support behind at most one candidate, but also allows a voter to distribute their vote weight to multiple candidates.
FPTP can be thought of as a [[Condorcet method]] where only a voter's 1st choice candidate among all candidates can receive votes in [[Head-to-head matchup|head-to-head matchups]]; in this formulation, the [[Smith set]] always contains the candidates who are tied for having the most votes.
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