When I posted about cabal equilibria in January, Jameson Quinn asked me
when honest voting is a cabal equilibrium. I thought about that question
recently, and for Condorcet methods I have a partial answer.
If there exists a double Condorcet winner, then an honest vote is a
cabal equilibrium.
A double Condorcet winner is a candidate who is preferred over every
other pair of candidates by a majority. That is, if C is the winner,
then for any other pair of candidates {A, B}, the set of voters who
ranked C above both A and B comprises a majority of the electorate.
The proof is posted to my blog here: http://www.spaceandgames.com/?p=134
- Peter de Blanc
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