I would agree with you if we didn’t have a two party majority and FPtT voting. You would also have to have a strong third party candidate that most people are excited about and is not trying to be a spoiler. You also will need to start persuading those you have mentioned who “are third party without knowing it” way before the election. Also getting a majority for a third party in the electoral college.

I want to be wrong and am willing to be convinced. I am curious how you see third party as an option with or without voting reform and how to persuade people to consider it.