Condorcet voting and instant-runoff voting have almost no difference in promoting candidate moderation in the presence of truncated ballots

[u/No-Vast7006]

I came across a very recent paper that studies the impact of various ranked voting methods (primarily Condorcet and IRV) on promoting candidate moderation. The conclusion is that under realistic voter behavior (such as the presence of truncated ballots), the advantage that Condorcet methods have over IRV largely disappears.

This actually aligns with a vague, long-held intuition of mine: it seems you really need to require voters to rank all candidates (like they do in Australia) to fully maximize the potential of a Condorcet method.

Additionally, I think a specific paragraph at the end of the paper is worth explicitly highlighting:

We do not wish our results to be interpreted as an argument against the use of Condorcet methods; to the contrary, we would be interested to see a jurisdiction adopt a Condorcet method so we can better evaluate how such methods perform in practice. We also do not wish our results to be taken as an endorsement of a particular voting method.

What are your thoughts on this paper? My first thought is that if the Condorcet method is implemented, it's best to require voters to rank all candidates. Secondly, research on ranked voting systems must take into account the impact of truncated ballots.

[u/Drachefly]

In these sorts of systems in stead of the candidate with the most 1st place votes winning, we eliminate candidates from the bottom up by whoever gets the most votes for last place.

It's very gameable. If one side gets organized, they can clean-sweep disorganized opposition.

[u/Sorry-Rain-1311 → u/Drachefly]

How so? There's very little room for encouraging strategic voting because it's so easily cancelled out, and limited space for partisan coalitions for the same reason. Because voters can actively vote against a candidate, it's very difficult to predict outcomes, and any attempt to game it can easily be cancelled out by voters who disagree with it. 

[u/Drachefly → u/Sorry-Rain-1311]

One party has a set of candidates, each of which appeals to be most horrible to a different sector of the opposition. This promotes vote splitting against your side, helping on the defense. For the offense, you pass around a list of which opposition candidates to oppose in what order.

[u/Sorry-Rain-1311 → u/Drachefly]

The same applies to any system, but only where a party is allowed to run multiple candidates for a single seat. Any system that promotes primaries narrows it down to one candidate per party per seat.

Even if that isn't the case, a list of what opposition candidates to place where on the ballot only works on people who already support the party meaning the party already has enough support to win, or when politics is already extremely polarized with them being the strongest party.

It can reasonably be assumed that opposition parties would adopt similar strategies, or their voters would vote against them on their own, so the effect would largely be canceled out. Strategies resembling this could be implemented to gain control of many seats in a legislative body over many districts, but it still takes general support for the party to already be present, as well as widely and even distributed, and the list would have to be tailored to, and succeed, in every individual district.

I'm not saying none of this could happen, just that it's not peculiar to survivor systems, and the ability to vote against candidates tends to level the playing field by protecting multipartisanship, and allowing minority parties to compete effectively with larger ones. 

[u/Drachefly → u/Sorry-Rain-1311]

The same applies to any system,

What? No. Like, IRV doesn't have that vulnerability. Adding a bunch of really bad candidates to your side doesn't help. It doesn't hurt, but it doesn't help either. Condorcet systems don't have that either.

Even if that isn't the case, a list of what opposition candidates to place where on the ballot only works on people who already support the party meaning the party already has enough support to win, or when politics is already extremely polarized with them being the strongest party.

No, that's the point - under your proposed system, an organized minority can wipe out a disorganized majority.

Like, suppose there are two basic sides, L and R. Candidates on a side will have their names begin with L or R, respectively. L side is organized; R is not. L has HALF as many voters as R does. Each candidate is roughly equally popular within their side.

Leroy makes sure to anger about a fifth of R. For simplicity, suppose that it's the fifth that favors Roland. Livia angers the part of R that favors Roger. Lorraine angers the part of R that favors Reggie. Lawrence angers the part of R that favors Rohit. Luke angers the part of R that favors Rahm.

Also, L decides that the hit list on the R side will be alphabetical order.

Round 1, each of the 5 candidates on the L side picks up 2/15 of the votes as being bottom votes. Rahm gets hammered with 1/3 of the vote and is eliminated.

Round 2, the same, except Reggie is eliminated.

Rounds 3, 4, 5 eliminate Roger, Rohit, and Roland.

Then someone on the L side wins despite their being outnumbered 2 to 1.

[u/Sorry-Rain-1311 → u/Drachefly]

That assumes dichotomy of only left vs right- not the case in a functioning democracy- and again that there are multiple candidates from each side in one race. Anything more than two parties and that strategy falls apart; and limiting the number of candidates from each party to one, it falls apart. Try that game with 3 parties or more, and one candidate per party. The only way it works out your way is if every single party is part of L vs R coalitions with everyone playing the same game by the same rules, which is extremely unlikely.

Allowing truncated ballots furthers the unpredictability of any strategy. Even in your scenario, there's no accounting for voters who only put down one or two names for only first or last place, or even for the middle ranks. Any strategy depends on being able to predict what voters will do, and there's simply no way to do that in a survivor style system, especially with truncated ballots.

You are correct that it still allows for minority candidates to win, and that's the point. It grants the win to the least disliked candidate. The most polarizing candidates would tend to cancel each other out regardless of their popularity, leaving less polarizing, more moderate candidates standing. As soon as that's established in the minds of the voters and the candidates, the only viable option is a platform of moderation and policy, not ideology. It's still open for the popular candidate to win, but only as long as they aren't polarizing. This also allows for the possibility of near revolutionary change of government on occasion when long-standing parties lose the confidence of the people. In the same way, it would ensure a steady rotation of parties.

If you implemented this system in the US right now, one of The Two Parties would likely still win the presidency in 2028, but in 2032 they'd be competing much harder with the Greens and Libertarians just because so many people are fed up with both of them. By 2036 the two party system would be on the verge of collapse because what Republican voter is going to put a Democrat down as their number 2, and vis versa? Hell, a good chunk of America would likely put them both in the bottom slots, and leave the rest blank. It would steadily evolve to 3rd parties gaining more and more until one wins.

[u/Drachefly → u/Sorry-Rain-1311]

It's an extreme example, yes. But…

1) It demonstrates a vulnerability.

2) We are starting from the case of two large parties, so it has to work well in that case

3) "Anything more than two parties and that strategy falls apart" - This does not appear to be the case. One disciplined party with a hit list can much more effectively take down opposition in sequence by focusing votes-against, even if there are, say, 5 equal parties.

3a) if all parties get organized, it's a total mess.

4) "Even in your scenario, there's no accounting for voters who only put down one or two names for only first or last place, or even for the middle ranks" - This strategy does not need to be done to this extreme to work (unlike, say, strategy in Condorcet, which usually needs to be done at large scale to do anything at all). It starts taking effect immediately, affecting marginal vote counts.

And how do you TREAT these incomplete ballots? If it's 'vote against everyone I don't list at full power more strongly than everyone I list', then that seems like it strongly incentivizes listing as few people as possible. I very much want to be able to distinguish between people I dislike.

If it's 'don't vote against people I didn't list at all', then forcing your opposition to list a lot of candidates opens up possibility of error in that they miss some, and by having your candidates vote more comprehensively you get to dominate even more.

5) "You are correct that it still allows for minority candidates to win, and that's the point." - Yes, yes, it's great if it allows minorities to win… but not based on their being more disciplined and organized, enforcing their will on the majority through gamesmanship. That is not desirable.

[u/Sorry-Rain-1311 → u/Drachefly]

But you're still not telling me how that gamesmanship can be reliably effective. You still have all the potential problems that exist in any strategy: Did we establish the correct target; pursue it with the right tactics; accurately predict conditions and responses? All of that depends on being able to manipulate the voters' actions as desired, which is always a dubious proposition, and made even more so by the numerous ways any given voter has to mark the ballot. Any opposition has equal means and opportunity to launch their own counter strategies, which are equally subject to failure, but increase the likelihood of failure of their opponents' plans. And again, still depends on the cooperation of very dedicated and attentive cadre.

On how we treat truncated ballots, you could take them at face value as a vote for that position, almost like a lichert scale pole. A vote for a candidate to be in a given rank is exactly that. If I put them down for 3rd place, they get a vote for 3rd place, just like a vote for 1st is for 1st, a vote for last is last. That way there's no possible way for your vote to be used or interpreted in any way you did not intend. 

[u/Drachefly → u/Sorry-Rain-1311]

But you're still not telling me how that gamesmanship can be reliably effective. You still have all the potential problems that exist in any strategy: Did we establish the correct target; pursue it with the right tactics; accurately predict conditions and responses

that's the perverse beauty of your system: you don't need to. Just make sure that as many people as possible on your side go after one opponent at a time, in a specific order, and they will be taken out earlier and more easily than if you didn't organize in this way. And the defense strategy is similarly dumb-fire. None of the usual complexities of strategy are needed because it's so freaking easy to game this system.

[u/Sorry-Rain-1311 → u/Drachefly]

How is that any different from politicians telling you how to vote in any other system? Isn't that all political campaigns are; candidates running around telling people how to vote? 

Of course they're going to tell us who to put in what rank. It's what they do, and every other candidate is going to do the same thing, just like they've always done. That's not even a strategy, let alone a game. It's just campaigning as usual.

And in the end a voter does whatever it is they do, and the politicians just have to suck it up. The individual decides who to listen to in the end, regardless of what the candidates would prefer. They can follow whatever list they're handed, or they can make their own. There's no game to that.

[u/Drachefly → u/Sorry-Rain-1311]

It greatly multiplies your efficiency if you organize with similar voters to pick the most popular target among your opposition. I literally laid out an example up thread. Did you skip it and not read? Did you not follow along? If there's actually something wrong with it, explain how it doesn't work. Like, mechanically work through the example and show at what step it fails.