Condorcet Methods - When, Why and How?

Abstract

Geometric representations of 3-candidate profiles are used to investigate properties of preferential election methods. The representation visualizes both the possibility to win by agenda manipulation, i.e. introducing a third and chanceless candidate in a 2-candidate race, and the possibility to win a 3-candidate election through different kinds of strategic voting. Here the focus is on the "burying" strategy in single-winner elections, where the win is obtained by ranking a main competitor artificially low. Condorcet methods are compared with the major alternatives (Borda Count, Approval Voting, Instant Runoff Voting). Various Condorcet methods are studied, and one method is proposed that minimizes the number of noncyclic profiles where burying is possible.