I’m more worried about the field of voters who went with McCain last time.
I can't speak for others but in 2008 I was resigned to merely casting my vote against Obama until Sarah joined the ticket and gave that speech at the convention. All of a sudden I had someone to vote for, even if it meant I'd have to go "with McCain". I don't think you have to worry except perhaps about the primary crossovers who seem to aid in giving us McCain-esque RINOs.