[EMAIL PROTECTED] wrote:
Kevin, I know that you have studied Top Two Runoff more deeply than I have. Here in Oregon measure 65 was defeated recently. It was a version of top two runoff in which the the first round of the runoff replaced the traditional primaries, i.e. it was cast as one grand open primary for all parties and all voters, from which the top two vote getters advance to the other stage in November. It was interesting that the IRV organization FairVote was against the measure, even though there was no IRV initiative on the ballot. It seems to me that Top Two Runoff might be more manipulable than the instant version of the same, since voters could vote insincerely in the first round without having to worry about that messing up their choice in the other stage. I would be interested in your thoughts on this matter.
I'm not Kevin, but I think I can comment. In any method that's [some base method] + runoff, where the runoff candidates are picked from the social ordering of the base method, the existence of the second round would increase the incentive to strategize.
However, it would not make it safe to always strategize. Say that the runoff method is "pick first and second place winners of the base method". Then any strategy that boosts your preferred candidate to either first or second place can be used - but if the strategy, when applied too greedily, causes both first and second place to be replaced by candidates you don't like, there's an incentive to be careful.
That's weaker than it is for just applying the base method and picking the winner. If you use strategy in the base method case, and you displace your true winner in favor of someone that you really loathe, then you're out of luck. For that to deter you from using strategy in a runoff, it has to displace both the candidates that would get into the runoffs.
One should also be aware that the second round, taken as a separate election, will be honest. That's because there are only two candidates and a simple majority election is strategyproof in that case. So that may weight against the increased incentive to use strategy in the first round. Whether this makes the method (in general) more fragile (attracting more strategy) or more robust depends on which component is stronger: the incentive to strategy in the first round, or to honesty in the second. That probably depends on the base method.
There may also be inter-round strategy. Say that there are two wings and a center. In the first round, the left wing runs a strategy. It's discovered. Now, the centrists may support the right-wing candidate in the second round "just to show them", whereas they wouldn't otherwise. To the degree that runoffs are two elections, such effects may occur.
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