re: Who has the most realistic chance to be the next Republican President?

Honestly, the three people who scare me the most as a Dem would never make it out of the Republican primary- Rubio (if immigration reform had gone through he could have destabalized the Obama coalition and chipped off some Hispanic voters, as it is now, the GOP has essentially cosigned itself to demographic irrelevance by 2024 or so when states like Texas and Arizona become Blue states) ; Christie (actually really conservative on Social issues-- he's pro-life for example but will never get the nuts to believe that); Rand Paul (assuming he is able to get away with his current dance of being socially libertarian when pitching to young voters and socially conservative when pitching evangelicals-- if he gets pinned down and the primaries would do that he'll have to sacrifice one of the two constituencies).