I don't think the GOP has a problem voting for a minority they view as an uncle tom (not saying Rubio is one, saying this might be how some in the GOP view him).
That's not what I'm saying. I'm saying that they'll jump on any opportunity to interpret liberal criticism of Rubio or of Republicans nominating Rubio as a claim that Rubio is an Uncle Tom. They're not going to pass up an opportunity to get on their high horses about reverse racism and real racists and so on.
Remember two things:
1. They've been convincing themselves for years that Obama's only popular because he's black and that Obama constantly "plays the race card" to evade legitimate questions/criticism.
2. They will not scruple to do something that they think is wrong if they see political advantage in it. Or at least they're very good about reversing their political principles when convenient, or they won't scruple to justify it as "turnabout is fair play" or similar.
Therefore, expect them to try trotting out really ham-handed parodies of race card style defenses of almost any criticism of Rubio, if he is nominated. Conservative commentary about Palin and women is probably a good preview, except they're even crazier now.