Informed majority coalition criterion

The informed majority coalition criterion (InfMC) or conditional majority determination criterion is a voting method criterion that is a weaker form of the majority criterion. It can be stated as follows:

A group comprising a majority of voters is always able to cast their votes so as to elect any candidate they wish, provided that the votes of the remaining minority are known to them and don't change.

It was independently defined by James Green-Armytage and Durand et al. Any voting method passing the majority criterion automatically passes the informed majority coalition criterion, since the majority can all vote their preferred candidate first to make that candidate win.

Range voting and the Borda count also pass the informed majority coalition criterion, even though they fail the majority criterion. Anti-plurality voting fails.

The informed majority coalition criterion is of importance when considering the implications of modifying a method to always elect an absolute majority-strength Condorcet winner if one exists. Such a modification can never make a method susceptible to strategic manipulation in more elections than it was before being modified. However, such a modification can change what strategy it's vulnerable to in those elections where it's manipulable.

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