I don't see the difference between "an imaginary world" and "an imaginary scenario, but according to the rules that actually apply in real world". If I were in that scenario, I would behave as you suggest I ought to, but I am not and will not be in that scenario. I never disputed that my vote matters, just precisely how much, and for what reasons.

I agree that it's really an ethical decision, which is why I closed with "How is a consequentialist to vote?"--my philosophical stance being consequentialist in nature. Whether it is "ethical to implicitly depend upon others doing something, without doing it yourself when it's your responsibility at a particular moment?" Calling it "my responsibility" seems to beg the question. Furthermore I wouldn't say I "depend" on others doing something, but rather that I "act according to" others doing something, that I empirically expect them to do. Many schools of philosophy would object to my framing here, but I have found these objections unpersuasive.

> If I were in that scenario, I would behave as you suggest I ought to

Ah, but you don't know if you're in that scenario or not, until other people actually go and vote.

Now, you empirically expect them to do so... but if your response to them doing what they do (i.e. go and vote) is to not vote, and you consider that a rational choice, then why shouldn't others also follow it? And if your ability to make that rational choice is enabled by those others not making a rational choice, I feel like there's still an ethical conflict here, even if you're purely reactive (i.e. is it ethical to rationally "cash in" on irrational, self-harmful choices of others?).

I do know that I'm not in that scenario, in the same sense as I know most things, like that next time I flip a coin it won't land on edge.

> if ... you consider that a rational choice, then why shouldn't others also follow it?

But this doesn't affect my reasoning, because whether or not I consider it rational, or whether or not I do it, does not affect whether or not they do it[1]. Along the same lines, I see no problem "cashing in" on other's irrational choices in general, provided that I am not causing or contributing to them making those choices.

[1] It may affect their behavior in future elections however. It is because of effects along these lines that I ultimately think I should vote.