Charles Munger, Jr. Explains Why Condorcet Systems Make Elections Fairer, More Stable, and Harder to Manipulate than IRV
In “Tactical Voting in Three-Candidate Polar Elections under Instant Runoff and under Condorcet Methods,” Charles T. Munger, Jr. investigates how resistant different voting systems are to tactical voting, which occurs when voters cast a ballot that does not reflect their sincere preferences. Using mathematical proofs and geometric modeling, Munger demonstrates that Condorcet methods are far more secure than Instant Runoff Voting (IRV) in preventing tactical voting from changing the election winner and in limiting large political shifts caused by manipulation.
Condorcet methods are resistant to manipulation because they determine the winner through pairwise comparisons of candidates rather than elimination rounds, basing the outcome on mutual majorities centered around the median voter in the electorate. When voters cast tactical ballots under a Condorcet system, those changes affect many pairwise contests at once, making profitable strategies unpredictable, symmetric, and largely self-neutralizing. In contrast, IRV relies on elimination order, which gives small, organized groups asymmetric leverage to tip the outcome.
Munger’s Perfect Defense Theorem shows that under Condorcet methods, attempts to change the outcome through tactical voting always fail if the defending side mobilizes the same fraction of tactical voters as the attacking side. In other words, if both factions play the tactical game equally, the sincere result always prevails.
Even if the defending side does nothing, if the fraction mobilized by the attackers is small, opportunities to change an election outcome are rare. For example, in polarized elections where 10 percent of voters try to game the system in each of the 453 races for the U.S. House of Representatives, a Condorcet method would see perhaps one manipulated outcome every seventy years, and the ideological swing in that one outcome will be small. In contrast, IRV would allow small organized groups to swing several races every election cycle, and also to produce large ideological swings.
The Fourth Candidate Theorem extends this insight, showing that Condorcet systems also encourage outcomes near the median of voter opinion and promote political stability. If a fourth candidate enters a polarized three-way race and positioned near the median of voter opinion, a Condorcet system naturally elects that candidate, since in head-to-head matchups most voters prefer someone closest to the median over those further away. The fourth candidate becomes an overwhelming winner, relegating tactical voting among the other three candidates to an irrelevant struggle for second place. Under IRV, however, that same fourth candidate is almost always eliminated immediately for lacking enough first-choice votes, leaving the tactical struggle between the other three candidates not only alive but unchanged. Together, these theorems show that Condorcet methods resist manipulation and reward representation near the median of an electorate, while IRV remains vulnerable to strategic behavior and to extreme or polarizing outcomes.
The findings suggest that although both systems use ranked ballots, Condorcet methods provide greater stability, fairness, and resistance to vote-splitting and tactical exploitation and should therefore be strongly favored in electoral reform efforts. Condorcet methods that use ranked ballots and head-to-head matchups, like Consensus Choice, also have the advantage of being easier to administer and to explain the pairwise results than IRV. They are also simpler to audit, because you only need to verify a small number of clear, numerical margins showing how much each candidate beats another in head-to-head matchups.
