[EM] IRV vs Plurality

[Jonathan Lundell]

On Jan 9, 2010, at 9:23 PM, Abd ul-Rahman Lomax wrote:

> On the other hand, in one-third of nonpartisan top-two runoff elections, which IRV supposedly simulates, the runner-up in the primary goes on to win the runoff, a "comeback election," according to a FairVote study. It simply does not happen with IRV.

It's hard to know what to make of this claim, other than, "so what?" -- if what you're comparing to TTR is the IRV candidates with the highest first-choice ballots.

Presumably voters in TTR and IRV elections know the counting rules. The meaning of a first-choice IRV vote is not the same as a TTR first-round vote. One plausible interpretation: if a TTR primary results in A>B, A tends to have all the votes A is ever going to get, but B, in the runoff, gets all the "anybody but A" votes, and wins.

OTOH, A>B>... in the first round of an IRV election tells us considerably less, since the cost of voting for a non-poll-leader is considerably less than with TTR. It's entirely plausible, though of course not necessary, that the A:B first choice breakdown reflects the lower-choice breakdown of the other voters.