Dr. Ben Carson
But he will not be elected in the 2016 elections.
Carson will not be elected because he has never held office before and his first stop won't be the oval one. The GOP may have broken away from "next in line" but I don't think they're ready for never in line. Yes, Cain did well in the primaries--but that was psychotic. By 2016 the Republican party will either have gotten over its psychosis or they will nominate Carson (or someone like him--probably someone much, much worse) and lose.
Paul will not win the 2016 election because despite his EVOLution over his father's positions taking a more reasonable centrist stance his views on foreign policy will still be an anathema to the base. Also, he's still basically a libertarian ... and that won't happen. He will be very, very popular with the under 30 voting block but will lose hard with everyone else. Remember that his dad, gaming the system as hard and as expertly as possible, didn't win a single state in 2012. That was the height of his power. Paul will win a couple of states--like Maine. Maybe, I dunno, Oregon. It goes no further.
He's got bi-partisan cred that no one in the party even approaches. And, hey, by 2016 might we be ready for some bi-partisanship? We will be. But Chris Christie won't win the 2016 presidential election.
Was it his dreamy moonlight walk on the beach, arm in arm with President Obama just before Romney's disastrous election? Was it the man-love bromance they shared in the wake of Superstorm Sandy? Is it Christie's liberal views on things that might make blue-state Democrats (not to mention centrists across the nation) vote for him? No. It's not.
The Overton Window is the narrow range of ideas the public finds acceptable. It moves slowly and whatever is "within it" is what the public could accept in a president. Here is our state of affairs: