There are different types of tactical voting:
Compromising (sometimes favorite-burying or 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 a 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. This is arguably one reason for the continuation of the two party system in the United States, where many perceive that only major parties will realistically win office.
For instance, voters favoring radical left-wing economic measures may prefer voting for a moderate, social-democrat candidate so that a right-wing candidate does not get elected.
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, a voter may insincerely rank a strong alternative last in order to help their preferred alternative beat it.
Push-over or turkey-raising is a type of strategic voting in which a voter ranks a weak alternative higher, but not in the hopes of getting it elected. For example, in a bloc vote where multiple votes are required, a voter may insincerely vote for a candidate they perceive as unlikely to win, in order to help their preferred candidate win.
It has been shown that it is impossible for a voting method to be both strategy-free and deterministic. For example, the random ballot voting method, which selects the ballot of a random voter and uses this to determine the outcome, is strategy-free and non-deterministic.
Tactical voting is quite well known in United Kingdom elections. There are three main parties that are 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.
Most 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, and they 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.
In many cases, it is difficult to distinguish between tactical voting by voters, and its analog before the election. For all the same reasons that voters might decide to vote tactically, campaign donors and activists may decide to tactically support or not support candidates with their money and labor, thus leading to results similar to those caused by tactical choices by the voters.A campaign can be sunk before it ever starts because it fails to convince enough sympathetic people that the campaign is viable, and hence worth backing.
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. Labour Party politician Anne Begg considers tactical voting dangerous: [1]
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 does not permit preferences ('likes' or 'dislikes') to be stated at all, 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".
See also: primary election, Duverger's Law, political party, strategic nomination, Gibbard-Satterthwaite theorem, vote swapping
Types of tactical voting
Strategy-free voting methods
Examples
Rational voter model
Outside Influence
Views on tactical voting
Tactical voting in particular systems
Sources