In a two party system voting for the other party does make someone a Nazi.
It does if one of the parties is full of Nazis. Particularly the party that nominates them:
Neo-Nazi Arthur Jones wins Republican nomination for Illinois congressional seat
https://www.cnbc.com/2018/03/21/neo...ination-for-illinois-congressional-seat-.html
So if the GOP aren't Nazis, how come they nominate them?