Worse than The Worst IRV Nightmare Election In Existence


305 voters, 5 candidates.

1 A
1 E

Counts: A = 50, B = 52, C = 100, D = 52, E = 51. A is eliminated by a margin of one vote. B gains 49 votes. B = 101, C = 100, D = 52, E = 51.
Then E is eliminated by a margin of one vote. 50 votes transfer to D.
B = 101, C = 100, D = 102. C is eliminated by the margin of one vote.
B = 152, D = 151. B wins by one vote.
In EVERY ROUND, the election was within one vote. That means expensive recounts and lawsuits.

D is a spoiler. D drew away votes away from the centrist C. If two members of the DE party had instead artificially ranked C top, then D would get eliminated and then C would win over B by about 200-100. This tactical voting would have given the two voters a better outcome.

C was preferred over every candidate by about a 2:1 ratio. And the D party, which has been branded as a SPOILER, may drop out. Meanwhile A and E were too extreme to have any chance, so we end up with two party domination between B (and maybe A/E, until they get too greedy and become a spoiler again) and C.

The D voters were tricked in another way. The second place votes of the DCEAB voters were not counted because their first vote was still on D at the critical moment that eliminated C. IRV ignored their second place votes while giving notice to other voters’ second choice candidates.

The election is equivalent to this:
1 A
49 AB
52 B
51 CB
49 CD
52 D
50 ED
1 E
IRV never examined more than two layers in. Annoyingly, C was even ranked first or second by a majority of voters, but still lost.

Yep, just about every flaw that real world voters care about, happened.


Your example implies that Condorcet would be better than IRV in this case.

I agree.


I mean, C has by far the most support and is ranked third or above by every voter. If you think of AB as the leftists and DE as the rightists and C as the centrist OF COURSE C should win.

Let me make one quick change to make this even more nasty…