Re: Math, chemistry, engineering?
I really don't understand what you're getting at.
I vote for the individual whose victory I assess to be in the best interest of the nation (or locality). Not surprisingly, those are usually (but not always) my best interests, too.
I even voted for a Republican once, because I knew him personally to be an honest and competent Sheriff, and I did not know his Democratic opponent.
I do not waste my vote or my time on a purely symbolic candidate just to make a point.