If your argument is that from the politicians’ perspective they believe, or claim to believe, that people support them based on the amount of votes they receive while ignoring the context of what the other choices in that vote are, and use those votes as proof they should continue holding their current policies, then yes, that’s probably true. My reaction to this would be to say the proper place to give a politician “legitimacy” by voting for or against their policies while avoiding the negative consequences of a protest vote getting someone like Trump elected is in the primaries, not the general.