Worse than The Worst IRV Nightmare Election In Existence


#1

305 voters, 5 candidates.

1 A
49 ABCDE
26 BACDE
26 BCADE
51 CBDAE
49 CDBEA
26 DCEBA
26 DECBA
50 EDCBA
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.


#2

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

I agree.


#3

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…