Who is the most likely person to still be the Republican nominee? Mitt Romney. So Mitt Romney, obviously he's in a lot of danger in Iowa, he's a terrible phony, a repeated flip flopper, but the bottom line is because he didn't have a mistress slush fund, he doesn't hang around with mafiosos, and he didn't get a serial rapist out of jail because a bunch of anti-Clinton whack-jobs convinced him that the guy was a victim of the system, you have to assume Mitt Romney is still the one to beat in the Republican nomination battle...
Even if Clinton, certainly not my preference, wins the Democratic nomination, I'll cast my vote gleefully for her. Being so happy to vote against [insert eventual Republican nominee here] makes being happy to vote for someone almost superfluous.