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Tactical voting

From Academic Kids

In voting systems, tactical voting (or strategic voting) occurs when a voter misrepresents his or her sincere preferences in order to gain a more favorable 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 nondeterministic (that is, might not select the same outcome every time it is applied to the same set of ballots). For instance, the random ballot voting method, which randomly selects the ballot of a single voter and uses this to determine the outcome, is strategy-free, but may result in different choices being selected if applied multiple times to the same set of ballots.

However, although no practical method is strategy-free, 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.

Contents

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, a voter 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.

Burying is a type of strategic voting in which a voter insincerely ranks an alternative lower in the hopes of defeating it. For example, in the Borda count or in a Condorcet method, a voter may insincerely rank a perceived strong alternative last in order to help their preferred alternative beat it.

Push-over is a type of strategic 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

In United Kingdom elections, there are three main parties represented in the Parliament: the Labour party, the Conservative party and the Liberal Democrats. Of these three, Labour and the Liberal Democrats are most similar. 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.

In the 1997 UK General Election, the Democratic Left organised GROT - Get Rid Of Them - a tactical voter campaign. In 2001, the Democratic Left's successor organisation the New Politics Network organised a similar campaign tacticalvoter.net (http://www.tacticalvoter.net). 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 (http://www.tacticalvoting.com) who encourage tactical voting as a way of defusing the two party system and empowering the individual voter. In the 2005 UK General Election individuals set up tacticalvoting.net (http://www.tacticalvoting.net) to balance the tactical voting debate.

In the Ontario general election, 1999, strategic voting was widely encouraged by opponents of the Progressive Conservative government of Mike Harris. This failed to unseat Harris, and succeeded only in suppressing the New Democratic Party vote to a historic low.

Rational voter model

Academic analysis of tactical voting is based on the rational voter model, derived from rational choice theory. In this model, voters are short-term instrumentally rational. 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); voters have a set of sincere preferences, or utility rankings, by which to rate candidates; voters have some knowledge of each other's preferences; and voters understand how best to use tactical voting to their advantage. The extent to which this model resembles real-life elections is the subject of considerable academic debate.

Pre-election influence

Because tactical voting relies heavily on voter's 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. Most campaigns craft refined media strategies to shape the way voters see their candidacy. During this phase, there can be an analogous effect where campaign donors and activists may decide whether or not to support candidates tactically with their money and labor.

In rolling elections, or runoff votes, where some voters have information about previous voters' preferences (e.g. presidential primaries in the United States, French presidential elections), candidates put disproportionate resources into competing strongly in the first few stages, because those stages affect the reaction of latter stages.

Views on tactical voting

Some people view tactical voting as providing misleading information. In this view, a ballot paper is asking the question "which of these candidates is the best?". This means that if one votes for a candidate who one does not believe is the best, then one is lying. British Labour Party politician Anne Begg considers tactical voting dangerous: [1] (http://news.bbc.co.uk/1/hi/uk_politics/1091208.stm)

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.

While most agree that tactical voting is generally a problem, there are some cases when a strictly limited amount of it may bring about an more democratic result. Since Arrow's impossibility theorem proves that any voting system is arguably undemocratic in at least some case, tactical voting may be used to correct such flaws. 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. An electorate using one of these two systems but which (in the general or the specific case) preferred the characteristics of the other system could consciously use strategy to achieve a result more characteristic of the other system. Under Condorcet, they may be able to win by "burying" the compromise candidate (although this risks throwing the election to the opposing extreme); while under IRV, they could always "compromise".

The problem is that such tactical voting would tend to overshoot and give undesired results. This greatly complicates the comparative analysis of voting systems. If tactical voting were to become significant, the perceived "advantages" of a given voting system 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. Ralph Nader refers to this as the "least worst" choice, and argues that the similarity of parties and the candidates in first past the post systems grows stronger due to the need to avoid this disapproval.

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 in turn allows for "voting against" a certain despised candidate without having to guess at whom the strongest contender is to defeat that candidate. Such a system would also serve to reduce the spoiler effect.


Approval voting

Steven Brams and Dudley R. Herschbach argued in a paper in Science magazine in 2000 that approval voting was the system least amenable to tactical perturbations. 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. A similar exaggeration can be given in the inverse by granting approval to unliked candidates, in order to ensure that a strongly disliked candidate doesn't win - compromising.


Instant runoff voting

Instant runoff voting has a somewhat reduced incentive for the compromising strategy, plus a minor vulnerability to the push-over strategy.


Condorcet

Condorcet methods have a further-reduced incentive for the compromising strategy, but they have some vulnerability to the burying strategy. The extent of this vulnerability depends on the particular Condorcet method. Some Condorcet methods arguably reduce the vulnerability to burying to the point where it is no longer a significant problem.


Borda

The Borda count has a both a strong compromising incentive and a large vulnerability to burying.


Single Transferable Vote

The compromising incentive in Single Transferable Vote systems is substantially reduced as the number of candidates to be elected is increased. Some forms of STV allow devious voters to gain an advantage by listing a candidate who is very likely to lose in first place. Meek's method essentially eliminates this strategy.


See also


External links

  • Tactical Voting Can Be a Weak Strategy (http://emptymoat.blogspot.com/2004/07/tactical-voting-can-be-weak-strategy.html) -- Article on tactical voting within larger strategic considerations
  • tacticalvoting.com (http://www.tacticalvoting.com) - Tactical Voting (for whatever reason) in the General Election 2005
  • tacticalvoter.net (http://tacticalvoter.net/?show=about&PHPSESSID=db7f6a5f3610d425c2094608542e1e1d) -- UK Tactical Voting anti-Tory
  • VotePair.org (http://www.votepair.org) VotePair is a banding together of the people who started tactical voting online in the 2000 elections.
  • Voting methods page (http://fc.antioch.edu/~james_green-armytage/voting.htm) Includes extensive discussion of strategic voting in a wide range of real and theoretical voting systems.


Sources

pt:Voto tctico

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