The existence of other candidates is not the same thing as any of them having the slimmest chance in hell of winning, and the way our cursed voting system works, they’re going to end up drawing votes away from the “major” candidate that most closely aligns with them. As a result, the “major” candidate they most oppose has one less vote they need to overcome. That means that until and unless a 3rd party candidate manages to completely overshadow one of the major political parties, which is effectively never going to happen, a 3rd party vote is just one more vote your most opposed candidate doesn’t need to beat.
And no, 3rd parties are not going to overshadow the major parties. It’s just not going to happen. Look at the absolute dogshit circus that is Trump, look at how many lifelong Republicans have vowed to never vote for him, how he’s absolutely obliterated any little shred of legitimacy the GOP had as a governing party. Now recognize that with that utterly weakened, vulnerable position, that best chance ever, no 3rd party has managed to even come close to unseating them as one of the inevitable 2 contenders. If it hasn’t happened now, it won’t happen ever, not with FPTP voting.
Alaska has Ranked Choice voting.