The act of casting a vote in an election for a candidate with the best chance of defeating another candidate who would otherwise be the most likely to win. This generally occurs where the candidate of one's choice is highly unlikely to be successful, or where preventing a particular candidate from being elected is of greater importance.
In voting systems, tactical voting (or strategic voting) occurs when a voter misrepresents his or her sincere preferences in order to prevent the worst possible outcome.
Although it is desirable for a democratic system to encourage voters to express sincere preferences, it has been shown by the Gibbard-Satterthwaite theorem that any voting method which is completely strategy-free must be either dictatorial or nondeterministic (that is, might not select the same outcome every time it is applied to the same set of ballots).
However, although no practical method is strategy-free (nor dictatorial), 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
There are different types of tactical voting:
Compromising (sometimes "useful vote") is a type of tactical voting in which a voter insincerely ranks an alternative higher in the hope of getting it elected. For example, in the first-past-the-post election, voters may vote for an option they perceive as having a greater chance of winning over an option they prefer (e.g., a left-wing voter voting for a popular moderate candidate over an unpopular leftist candidate, or in order to help defeat a strong right-wing candidate.) Duverger's law suggests that, for this reason, first-past-the-post election systems will lead to two-party systems in most cases. In those Proportional representation systems that include a minimum percentage of votes that a party must achieve to receive any seats, people might vote tactically for a minor party to prevent it from dropping below that percentage, which would make the votes it does receive useless for the larger political camp that party belongs to.
Burying is a type of tactical voting in which a voter insincerely ranks an alternative lower in the hopes of defeating it.
Push-over is a type of tactical voting in which a voter ranks a perceived weak alternative higher, but not in the hopes of getting it elected. This primarily occurs in runoff voting when a voter already believes that his favored candidate will make it to the next round - the voter then ranks an unpreferred, but easily beatable, candidate higher so that his preferred candidate can win later. A United States analogy would be voters of one party crossing over to vote in the other party's primary to nominate a candidate who will be easy for their favorite to beat.
Examples in real elections
One high-profile example of tactical voting was the situation that led to the 2003 California recall. As California holds open primaries in which anyone can vote for any candidate he or she pleases, Davis supporters were rumored to have voted for Simon because Riordan was perceived as a greater threat to Davis; Many people who prefer the Liberal Democrats vote for the Labour candidate where Labour is stronger and vice-versa where the Liberal Democrats are stronger, in order to prevent the Conservative candidate from winning. Since then tactical voting has become a real consideration in British politics as is reflected in by-elections and by the growth in sites such as tacticalvoting.com who encourage tactical voting as a way of defusing the two party system and empowering the individual voter.
In the Canadian general election, 2004 and to a lesser extent in the Canadian general election, 2006, strategic voting was a concern for the federal New Democratic Party. In the 2004 election, the governing Liberal Party was able to convince many New Democratic voters to vote Liberal in order to avoid a Conservative government. The New Democratic Party leader Jack Layton would respond by asking voters to "lend" their votes to his party, suggesting that the Liberal Party would be bound to lose the election regardless of strategic voting.
In the 2006 local elections in London, tactical voting is being promoted by sites such as London Strategic Voter in a response to national and international issues.
Rational voter model
Academic analysis of tactical voting is based on the rational voter model, derived from rational choice theory. That is, voters are only voting in order to make an impact on one election at a time (not, say, to build the political party for next election); and voters understand how best to use tactical voting to their advantage.
Pre-election influence
Because tactical voting relies heavily on voters' perception of how other voters intend to vote, campaigns in electoral systems that promote compromise frequently focus on affecting voter's perception of campaign viability.
In rolling elections, or runoff votes, where some voters have information about previous voters' preferences (e.g.
Views on tactical voting
Some people view tactical voting as providing misleading information. British Labour Party politician Anne Begg considers tactical voting dangerous:
Tactical voting is fine in theory and as an intellectual discussion in the drawing room or living rooms around the country, but when you actually get to polling day and you have to vote against your principles, then it is much harder to do.Tactical voting is generally regarded as a problem, since it makes the actual ballot into a nontrivial game, where voters react and counter-react to what they expect other voters' strategies to be.
Though Arrow's impossibility theorem and Gibbard-Satterthwaite theorem prove that any useful voting system is prone to manipulation, some use game theory to search for some kind of "minimally manipulatible" voting schemes. For instance, under purely honest voting, Condorcet method-like systems tend to settle on compromise candidates, while Instant-Runoff Voting favors those candidates which have strong core support - who may often be more extremist. (This never applies to "sneakier" tactics such a push-over.)
Tactical voting greatly complicates the comparative analysis of voting systems. If tactical voting were to become significant, the perceived "advantages" of a given voting system (that is, tending towards compromise or favoring core support) could turn into disadvantages - and, more surprisingly, vice versa.
Tactical voting in particular systems
First past the post / plurality voting
Tactical voting by compromising is exceedingly common in plurality elections.
Due to the especially deep impact of tactical voting in first past the post electoral systems, some argue that systems with three or more strong or persistent parties become in effect forms of disapproval voting, where the expression of disapproval in order to keep an opponent out of office overwhelms the expression of approval to elect a desirable candidate.
One often-overlooked flaw in the first past the post system is that, in single member districts, voters can invariably select only one candidate, whilst in multi-member districts they can never select more candidates than the number of seats. Approval voting, by contrast, allows voters to cast a vote for as many candidates as they wish. This may be related to the fact that approval voting is designed to avoid preferences ('likes' or 'dislikes') being stated at all, instead permitting only a statement of tolerances, that is, "which candidate could you stand to see win", as opposed to "which candidate would you like to see win." Approval voting is vulnerable to tactical voting, however, as a voter can exaggerate his disapproval of a slightly unpreferred candidate by not ranking him in order to help ensure his most preferred candidate wins, analogous to the burying strategy mentioned above.
Instant runoff voting
Instant runoff voting has a somewhat reduced incentive for the compromising strategy, plus a minor vulnerability to the push-over strategy.
Single Transferable Vote
The compromising incentive exists in the Single Transferable Vote. If one feels the favoured candidate is certain to be elected in any case, insincerely ranking the second candidate first guarantees them a full vote if needed. However, the greater the certainty of the first candidate being elected, the bigger their likely surplus, the higher the fraction of the vote that would be transferred to the next candidate, and hence the lower the proportionate benefit of tactical voting.
More sophisticated tactics may be practicable where the number of candidates, voters and/or seats to be filled is relatively small.
Some forms of STV allow tactical voters to gain an advantage by listing a candidate who is very likely to lose in first place, as a form of pushover.
Tactical unwind
The term "tactical unwind" is used by some political scientists and commentators to refer to the phenomenon when tactical voting takes place in one general election but in subsequent elections voters revert to their normal patterns.
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