Comment by AnthonyMouse
1 day ago
> If this scenario isn't super weirdly convoluted, more of those votes shift to B than X, so X is eliminated next.
It doesn't have to be that convoluted, all it takes is for the eliminated candidate to be a moderate so their votes go in two different directions. But you're right that I messed up that example; the percentages are wrong.
The problem case is when your second most favored candidate would otherwise be eliminated first and you need to prevent that by causing your most favored candidate to be eliminated instead, because the second best candidate has a better chance in the next round.
Suppose the candidates you dislike, X and Y, are the first choice of 40% and 25% of people respectively, and then A and B split the remainder evenly. X and Y are the two extremists -- on opposite sides of each other, with the moderates A and B in the middle. You favor A but A leans in the direction of X and B leans in the direction of Y.
If B is eliminated first then half of B's support goes A but half goes to Y, Y is still ahead of A and then A is eliminated next. If A -- your preferred candidate -- is eliminated first, half their support goes to B and the other half to X but Y gets nothing. Y then loses to B and the final round is X vs. B rather than X vs. Y. And the elimination of Y puts all their support behind B since X is the opposite extreme. But only if you rank B above A even though that's not what you'd have preferred.
> Yeah that's a real issue, and I'd want to use condorcet methods to fix that.
But now you're no longer using RCV/IRV. Score voting is a Condorcet method.
> Meanwhile with approval or score voting, a lot of people pretend not to like the other party's moderate because they're trying to get their side to win and it gets really messy.
Except that doesn't really help them because doing that also makes it more likely that their least favorite candidate wins, which is a significant incentive not to do it. The only reason to do that is if you're confident your favored candidate could only lose to your second choice, in which case it was really a two candidate race to begin with.
> Is there a need to have multiple candidates per party? If there is, a two stage election that picks party first and then picks probably-the-moderate is probably better than anything.
It doesn't matter if they're in the same party or not. If you're using a voting system that allows more than two parties to be viable then you'll have similar candidates running from similar parties. "Force the election to be one candidate from each of two major parties" is FPTP and it's terrible.
> A B X Y
It's very unlikely that the two candidates I hate are on opposite extremes and both popular.
> Score voting is a Condorcet method.
That gains it a point but there are much better methods. Ones where I don't feel the need to balance risk versus reward for candidates I moderately dislike. Then the guarantee of the pairwise winner coming out on top is actually using accurate information on what everyone wants.
> Except that doesn't really help them because doing that also makes it more likely that their least favorite candidate wins, which is a significant incentive not to do it. The only reason to do that is if you're confident your favored candidate could only lose to your second choice, in which case it was really a two candidate race to begin with.
If I'm moderately confident then I'm likely to do it despite the risk.
> It doesn't matter if they're in the same party or not.
The whole framing of the problem was that one of the candidates in the minority party wins. If there are four unrelated candidates that problem goes away. The more popular moderate won, not a big deal.
> It's very unlikely that the two candidates I hate are on opposite extremes and both popular.
It's easy to hate the candidate on the opposite extreme from the way you lean, so all this really requires is for the extremist on your side to be a corrupt populist who gets support by telling people the lies they want to hear or is paying off the right people to get favorable media coverage or valuable endorsements. Or is just more extreme than you can accept but you're in a district with some people who want that.
Notice also that neither of these candidates are the first choice of the majority. They just have enough support in a >2 candidate race to not be the first knocked out.
> Ones where I don't feel the need to balance risk versus reward for candidates I moderately dislike.
This is Arrow's Impossibility Theorem again. All of them do that, because in the rock-paper-scissors triangle where no candidate can beat both of the others, you then need something equivalent to a score to choose the winner. At which point degrading your second choice hurts them against both your first and third choice and whether or not you should do that is influenced by how likely you regard it that other voters will favor your first choice over your third but not your second.
It's also a dangerous game because the error bars on polls are huge and it's more often than not that the final results are very different than anybody's wild guess from the day before they started counting the votes.
> If I'm moderately confident then I'm likely to do it despite the risk.
Suppose your true ratings would be 10 for your most preferred candidate, 7 for the second best and 1 for the inhuman monster the opposing tribe somehow supports for no explicable reason. Polls say your first choice is expected to score ~5, your second choice ~6 and your vile enemy ~4, but all of these are plus or minus 2 points or more because polls are practically random number generators. What are you going to do?
You have the option to try to tank your second choice to give your first choice a better chance, but it's still a very real possibility that your first choice ends up at 4 and the hated enemy at 5.
> The whole framing of the problem was that one of the candidates in the minority party wins. If there are four unrelated candidates that problem goes away. The more popular moderate won, not a big deal.
It's still the same, and the minority party candidate isn't necessarily that much of a moderate, they're just not a far extremist.
Suppose it's California and a Republican, a Democrat and a member of the Green Party are in the race. The district is 40% Republican and under the old system correspondingly 60% Democrat, but in a system with more than two viable parties, it's 40% Republican, 29.9% Democrat and 30.1% Green.
If you hold that election with RCV and the Democrat gets knocked out first, the moderate Democrats (which, with the Green candidate in the race, was all of them) have to choose between a California Republican and a Green Party candidate who proudly wants to raise the gas tax to $8/gallon and pull out of NATO. More than a third of the moderate Democrats choose the Republican over that and under RCV that becomes a Republican seat.
The same race with score voting only does that if people vote the way you seem to think they would, which is exactly their incentive not to.
> This is Arrow's Impossibility Theorem again. All of them do that
They do not. There are voting methods where I feel they work well enough that I don't worry about strategy, and I don't worry about what threshold to use for approval, I just rank choices honestly and then I'm done.
> Suppose your true ratings would be 10 for your most preferred candidate, 7 for the second best and 1 for the inhuman monster the opposing tribe somehow supports for no explicable reason. Polls say your first choice is expected to score ~5, your second choice ~6 and your vile enemy ~4, but all of these are plus or minus 2 points or more because polls are practically random number generators. What are you going to do?
In this situation the strategy play is that I rate both of the first two at 10. I'm not risking #3 by being strategic, I'm risking that I get #2 when I could have gotten #1.
For the situation where I might strategically lower the score, it's when there's a 10, there's a 7, there's a 4, and there's a 1. Do I give the 4 an honest rating that might help them win over the candidates I like, or do I give them a 1 and pray really hard that neither of the two guys I hate win? It's a tough choice.
> Suppose it's California and a Republican, a Democrat and a member of the Green Party are in the race.
This is a totally different situation. In the last version there were two moderates and one of them won. It was fine. In this version there's one middle candidate and they lose. But we already did this scenario earlier. I said "Yeah that's a real issue, and I'd want to use condorcet methods to fix that." So not just an instant runoff, but keeping the ranking system.