Paddy Power, the Irish betting website, Sen. Paul and Gov. Christie are tied at 9/2 odds with Sen. Marco Rubio in third at 5/1. As my British friend Jamie often says, "Have you ever met a poor bookie?" (I always respond that I've never met a bookmaker, period -- poor or otherwise. But I think you get the point.)
Personally, I just don't see Gov. Christie as a realistic candidate given his "bridgegate" troubles at home. But, on the other hand, it might make some sense: the nomination could come down to a tea party/establishment showdown with Paul the candidate of the former and Christie the favorite of the latter.
P. S. Always go with the establishment candidate.