Instant Runoff Voting and “core support”

Background

Rob Richie, evangelist for the Instant Runoff Voting (IRV) movement, claims that IRV elects “majority winners”. But what about situations like the 2009 IRV mayoral race in Burlington, Vermont? In that election, Democrat Andy Montroll was favored over Republican Kurt Wright 56% to 44% (930-vote margin) and over Progressive Bob Kiss 54% to 46% (590-vote margin), majorities in both cases. In other words, in voting terminology, Montroll was a “beats-all winner,” also called a “Condorcet winner” – and a fairly convincing one.

However, in the IRV election, Montroll came in third! Kiss beat Wright in the final IRV round with 51.5% (252-vote official margin).

Rob Richie excuses the fact that IRV can fail to elect a Condorcet winner in such cases, claiming that the Condorcet winner didn’t have enough first-place votes. Richie calls the first place votes “core support”. He says:

"Condorcet-type voting violates the principle of requiring a minimum level of core support by permitting a candidate to win who would not win a single vote in a plurality election.
Source

Counterexample

Contra Rob Richie, we now demonstrate a simplified IRV election scenario, in which one of the losing candidates was preferred by a majority of voters to the winning candidate, and received more “core support” than the winner.

 % of voters
their ranking
 35% W > Y > Z > X
 17% X > Y > Z > W
 32% Y > Z > X > W
 16% Z > X > Y > W

Instant Runoff Voting selects candidate X as the winner, beating W in the final round, 65% to 35%.

But wait!

A huge 67% majority of voters would rather have candidate Y than X. And Y received nearly twice as many first-place votes as X, 32% vs. 17%.

And an even larger 83% super-majority of voters would rather have candidate Z than X (and Z got just a little fewer first-place votes than X).

So the claim that IRV “elects majority winners” is seriously misleading.

Also…

The first row of voters have an incentive to betray W by pretending Y is their actual favorite – then they get their second choice instead of their last. W is a spoiler. If he would drop out of the race, then Y would win instead, even with no change in voter preferences.

The third row of voters have an incentive to betray candidate Y by pretending candidate Z is their favorite – then they get their second choice instead of their third.

The first row of voters made a big mistake by voting honestly. Suppose 20% of the voters, all from that bloc, had simply refused to vote. That would actually have been better for them than voting honestly, because it would have caused Y to win (whom they prefer over X). Their honest “X is worst” votes actually caused X to win!

Also, Y is the Condorcet “beats-all” winner, but doesn’t make it to the final round: 65% majority says Y>W; 67% majority says Y>X; 84% majority says Y>Z.

And W is the Condorcet “lose-to-all” loser, but makes it to the final round (65% majorities say others>W).

FairVote’s spin

The following excerpts are taken verbatim from FairVote’s web site.

There are many single winner election methods other than our existing plurality and two-round runoff voting systems. Here are reasons for why we believe that instant runoff voting (IRV) offers the most politically practical and common sense option for replacing the plurality voting and traditional runoff systems used in nearly all American elections.

  • Majority Rule: Plurality voting only rewards first choice support. With IRV, a candidate cannot win an IRV election without being acceptable to a majority of voters.
  • Requires Both Breadth and Strength of Support: Being acceptable to a majority of voters is not enough to win an IRV election. A candidate also must have enough first choice support to avoid early elimination. IRV does not reward candidates who avoid all controversial issues.
  • No Complex Strategies: Voters in IRV elections almost never face a “spoiler” dilemma no matter how many candidates run, which means they can vote their hopes and not their fears. IRV is essentially resistant to strategy, according to voting experts like Nicolaus Tideman.

Evaluating Alternatives to IRV

We highlight the following criteria to evaluate a single winner system’s merits and political viability ” IRV upholds all these criteria, while other leading reform options do not.

  • Does the system meet the common sense principle of requiring a minimum level of core support? A winner should be at least one voter’s first choice.
  • Does the system meet the common sense principle of rewards for sincere voting? A voter should not likely be punished for voting sincerely under the system’s rules.
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