The 1932 elections in Germany had three candidates: Hitler, Hindenburg, and Thälmann. The social democrats denounced Thälmann as being just as bad as Hitler and supported the "center-right" candidate Hindenburg as a lesser-evil. Hindenburg appointed Hitler as chancellor which enabled him to seize power, become a dictator, and slaughter the left.
If you think the lesson from that is that the communists were being unreasonable for refusing to back Hindenburg, the guy who historically won and brought about the rise of Hitler, then I don't know what to tell you. There was exactly one anti-Hitler candidate in that race.
So the lesson you take from that is that you shouldn’t vote? You are misreading the moment if you think that.
There is no viable third party. And under no circumstances will Harris put Trump in power. He is far more likely to end up in jail than in power if Harris win.
The lesson from nazi germany is that you do not let fascists take power