I think your first paragraph is true of voters in general, but US politics very specifically (and increasingly so). I think this election will be confirmed by which side is more entrenched in the 'won't vote for the other guy' camp.

I'd be surprised if they did that to be honest, though I think some will just skip voting for either. Although the only reason I can think anyone would vote for Trump is that he isn't a democrat. I really don't understand how he won the nomination (well ok I do, but I don't want to).