Tactical voting: Difference between revisions
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{{Wikipedia}}
In [[voting system]]s, '''tactical voting''' (or '''strategic voting''') occurs when a voter misrepresents his or her ''sincere preferences'' in order to gain a more favorable outcome. Any minimally useful voting system has some form of tactical voting, as shown by the [[Gibbard-Satterthwaite theorem]]. However, the type of tactical voting and the extent to which it affects the timbre of the campaign and the results of the election vary dramatically from one voting system to another.
== Types of tactical voting ==
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40 C </blockquote>A is the [[Condorcet winner]] here ([[Pairwise beat|pairwise beats]] B 30 to 25 and C 55 to 40). But if A-top voters vote A>C instead, then they can make A win in several [[Condorcet methods]], such as [[Schulze]], [[Minimax]], etc. This is because they start a [[Condorcet cycle]] where A has the weakest pairwise defeat of the three (A loses 30 to 40 to C, while B loses 25 to 70 to C and C loses 40 to 55 to A). This is an example of the [[chicken dilemma]].
Burying is often discussed in the context of [[Condorcet methods]], where it can be used to create strategic [[Condorcet cycle]]<nowiki/>s. Also see [[later-no-help]] for some examples of burying.
=== Pushover ===
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5 C1</blockquote>In any PR method that spends a Droop quota or more of ballots when a candidate is elected, A1 is likely to win first, and then at least 16.333 A voters' ballots will be spent, leaving them with 13.666 ballots to support A2. This allows B1 to win the second seat in most methods. However, if the A1 voters had split into two groups of 15 voters each, with one [[bullet voting]] (only voting for) A1 and the other only for A2, then they guarantee that both A1 and A2 win in most methods, because the two candidates have more votes each (15) than the other candidates (B1 with 14 and C1 with only 5), and when the votes in favor of one are spent, only the 15 voters who chose that candidate lose their ballot weight.
=== Other types of strategic voting ===
'''One-sided strategy''' is when only the side/[[faction]] that benefits from the strategy (i.e. those who [[Pairwise|prefer]] the candidate the strategic voting is intended to benefit to the candidates it is intended to hurt) votes strategically, while the side(s) that would be hurt don't.
==== Coordinated strategy ====
It's important to differentiate between ''coordinated'' strategy, and ''uncoordinated'' strategy, as well as informed strategy vs. uninformed strategy.
== Strategy-free voting methods ==
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Some common terms:
* Frontrunner/viable candidate: A candidate expected to have a significant chance of winning.▼
There are arguments about the best voting strategy to take in different systems, but the general consensus is:
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== Definitions ==
▲
'''Truncation:''' When a voter doesn't show support for some of their less-preferred candidates (i.e. an A>B>C voter truncates and only votes A>B or A).
'''Bullet voting:''' When a voter
'''Min-maxing:''' When a voter gives maximal support to some candidates (usually defined here as ranking or rating them all equally) and no support to all other candidates.
== Notes ==
Much voting strategy revolves around a voter deciding whether to back one of the frontrunners or not; this often reduces further to deciding which of 2 frontrunners to back, which results in essentially a [[head-to-head matchup]] between the two. This is often referred to as deciding whether to "vote for the lesser of two evils or waste your vote". One of the goals of voting reform is to allow voters to be able to be as sincere as possible in expressing their preference for nonviable candidates. ▼
=== Voting for the lesser of two evils ===
▲It's important to differentiate between ''coordinated'' strategy, and ''uncoordinated'' strategy, as well as informed strategy vs. uninformed strategy. For example, [[Approval voting]] and [[Score voting]] guarantee that at least half of the voters can force their preferred candidates to tie or win, and force their dispreferred candidates to tie or lose. However, this crucially hinges on these half of the voters of voters knowing a) that they all prefer those candidates, and b) that they all plan to use the strategy. Otherwise, those who attempt the strategy may either fail to support all of the candidates supported by the group of voters, resulting in the strategy not always working, or they may do it while not everyone else in the group does, which potentially weakens their own vote's ability to influence who wins among the candidates not maximally preferred by that half of the voters. So strategy comes in difficulty levels of execution.
▲Much voting strategy revolves around a voter deciding whether to back one of the frontrunners or not; this often reduces further to deciding which of 2 frontrunners to back, which results in essentially a [[head-to-head matchup]] between the two. This is often referred to as deciding whether to "vote for the lesser of two evils or waste your vote". One of the goals of voting reform is to allow voters to be able to be as sincere as possible in expressing their preference for nonviable candidates.
=== Information in strategic voting ===
An important thing to consider with strategic voting is how difficult it is for voters to figure out how to strategically vote. Distinctions are made between zero-info strategy (strategy that can be applied to get a better result without any information of other voters' preferences) and strategies that revolve around having various amounts of (accurate) polling information. In addition, the likelihood of a strategy working, and the risk/amount of harm (see [[utility]]) coming from it backfiring is also studied. Another common measure of a voting method's resistance to strategic voting is manipulability, which measures how often a voter or group of voters can vote strategically to improve the election results from their point of view.
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