Strategic voting

Proportional representation systems with small districts often involve large-scale vote management operations, which are common in countries using STV-PR such as Ireland.

[2][12] Michel Balinski and Rida Laraki, the inventors of the majority judgment method, performed an initial investigation of this question using a set of Monte Carlo simulated elections based on the results from a poll of the 2007 French presidential election which they had carried out using rated ballots.

[15] Switching from a method that is highly manipulable to one that is more resistant would help discourage widespread strategic voting, all else equal.

[19] Polls are then a tool used by voters to ensure that the minority candidate doesn't obtain office, which would be adverse to Duverger's law.

In the former situation, electors make their own judgement as to the most effective way to (typically) prevent the election of a specific candidate or party.

The form that coordinated tactical voting takes depends largely on the electoral system of the polity.

An intermediate case also exists, where a non-party campaign attempts to coordinate tactical voting, typically with the goal of defeating a certain party.

Cases of this include the Canadian Anything But Conservative campaign, which opposed the Conservative Party of Canada in the 2008 and 2015 federal elections, or the Smart Voting campaign organized by Russia's Anti-Corruption Foundation with the goal of opposing and weakening the United Russia party in the 2021 Russian legislative election.

[24] In the 1999 Ontario provincial election, strategic voting was encouraged by opponents of the Progressive Conservative government of Mike Harris.

This failed to unseat Harris but succeeded in suppressing the Ontario New Democratic Party vote to a historic low.

In at least two closely-contested ridings, strategic voting websites obtained enough pledges to account for the victory margin of the Liberal candidate.

In Germany the share of strategic voters was found around 30%, which decreased to 9% if only non-allied party candidates were contenders for the electoral district winner.

][dubious – discuss] In 2016 Hong Kong Legislative Election, the practices of strategic voting were expanded by Benny Tai's Project ThunderGo.

[41] In the 2023 Polish parliamentary election, websites like pogonimypis.pl[42] (meaning "We'll chase the PiS") gave information for which voters should vote for in their constituency in order to maximize the chance of the opposition winning the extra seat.

At the same time, a referendum with the questions asked in a persuasive way took place, with the oppositing recommending to not take the referendal card.

While it is hard to prove that GROT swung the election itself, it did attract significant media attention and brought strategic voting into the mainstream for the first time in UK politics.

[citation needed] In Northern Ireland, it is believed that (predominantly Protestant) Unionist voters in Nationalist strongholds have voted for the Social Democratic and Labour Party (SDLP) to prevent Sinn Féin from capturing such seats.

[53] Strategic voting was expected to play a major role in the 2019 General Election, with a YouGov poll suggesting that 19% of voters would be doing so tactically.

However, it resulted in the lowest gubernatorial general election turnout in modern California political history, thus requiring fewer signatures to qualify a recall that ultimately ousted Davis.

Pedro Rosselló, the New Progressive Party's candidate of that year, was unpopular across much of the territory due to large corruption schemes and the privatization of public corporations.

The elections were close; statehood advocates won a seat in the U.S. house of representatives and majorities in both legislative branches, but lost governance to Aníbal Acevedo Vilá.

Analysis of strategic voting is commonly based on a model of behavior where voters are short-term instrumentally rational.

In this special case, the pij pivot probabilities are all equal and the rules for the specific voting methods become: Myerson and Weber also describe voting equilibria that require all voters use the optimal strategy and all voters share a common set of pij pivot probabilities.

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 time.

For instance, when electors vote for their own preferences rather than tactically, Condorcet method-like methods tend to settle on compromise candidates, while instant-runoff voting favors those candidates with strong core support but otherwise narrower appeal due to holding more uncompromising positions.

Thus, Condorcet methods incentivize candidates to position themselves closer to the median voter and appeal to a wider section of the electorate than instant-runoff voting does.

Systems like instant runoff that pass later-no-harm but fail participation still incentivize truncation or bullet voting in some situations.

Steven Brams and Dudley R. Herschbach argued in a paper in Science magazine in 2001 that approval voting was the method least amenable to tactical perturbations.

If many different groups voters use this strategy, this gives a paradoxical advantage to the candidate generally thought least likely to win.

[72] Some forms of STV allow strategic voters to gain an advantage by listing a candidate who is very likely to lose in first place.