Strategic or tactical voting is voting in consideration of possible ballots cast by other voters in order to maximize one's satisfaction with the election's results.

Gibbard's theorem shows that no voting system has a single "always-best" strategy, i.e. one that always maximizes a voter's satisfaction with the result, regardless of other voters' ballots. This implies all voting systems can sometimes encourage voters to strategize. However, weaker guarantees can be shown under stronger conditions. Examples include one-dimensional preferences (where the median rule is strategyproof) and dichotomous preferences (where approval or score voting are strategyproof).

With large electoral districts, party list methods tend to be difficult to manipulate in the absence of an electoral threshold. However, biased apportionment methods can create opportunities for strategic voting, as can small electoral districts (e.g. those used most often with the single transferable vote). Proportional representation systems with small districts often involve large-scale vote management operations, which are common in countries using STV-PR such as Ireland.

Some types of strategic voting described in the literature are:

Strategic voting is highly dependent on the voting method being used. A strategic vote which improves a voter's satisfaction under one method could have no effect or be outright self-defeating under another method. Gibbard's theorem shows that no deterministic single-winner voting method can be completely immune to strategy, but makes no claims about the severity of strategy or how often strategy succeeds. Later results show that some methods are more manipulable than others.

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. Comparing range voting, Borda count, plurality voting, approval voting with two different absolute approval thresholds, Condorcet voting, and majority judgment, they found that range voting had the highest (worst) strategic vulnerability, while their own method majority judgment had the lowest (best). Further investigation would be needed to be sure that this result remained true with different sets of candidates.

Party-list proportional methods typically show less strategic voting, although the existence of electoral thresholds can lead voters to vote strategically to avoid wasted votes.

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