This is bigger than just the math of this election.
Our votes will be analyzed, the platforms of the candidates will be analyzed, just because this election is lost, does not mean that votes for the losers were entirely worthless.
By voting for who I actually want and not voting defensively when I don't support any of the major candidates, I am making my voice heard. Maybe not for this election, maybe not for the next, but my hope is that eventually the main 2 parties will take notice and adopt some of the policies from "lesser" candidates that end up with a non-profit amount of votes.
Consider a hypothetical situation where the vote is between two major candidates, one of which is utterly corrupt, but can be relied upon to at least preserve the existing system, while the other one is running on a platform that is likely to preclude fair elections in the future altogether (in some countries, this is a real thing - when Russia voted Putin in back in 2000, that was exactly the choice on the table).
Now, if your long-term strategy is to keep voting against both to draw attention, you'd have to treat such an election as a special case, because if the "greater evil" wins, you cannot continue with your strategy in the next cycle at all. So it would be in your self-interest to vote for the "lesser evil".
This case is fairly clear, because the advantages and disadvantages are easy to compute, being on the same scale (affecting the power of your vote). But the same arithmetic applies to issues on different scales, too, so long as you have some sort of preferential ranking for those scales, so that you can unify them.
For example, you might want your vote to have more power, but you might also want to ensure that there's no repeat of something like the Japanese-American internment. If the latter is more important for you than the former, and it comes up as an issue in one particular election, it would be more important to vote strategically in a way to prevent it, even if it doesn't advance (and possibly sets back) your other goal.
Ranking the scales is subjective, of course. I'm not saying that this election is necessarily like that from your perspective. But I urge you to at least consider that possibility - tally up all the effects of either major candidate winning, and see how that stacks up against the beneficial effects of adopting some of the policies of "lesser" candidates in distant future, as well as probability of that adoption.
Our votes will be analyzed, the platforms of the candidates will be analyzed, just because this election is lost, does not mean that votes for the losers were entirely worthless.
By voting for who I actually want and not voting defensively when I don't support any of the major candidates, I am making my voice heard. Maybe not for this election, maybe not for the next, but my hope is that eventually the main 2 parties will take notice and adopt some of the policies from "lesser" candidates that end up with a non-profit amount of votes.