"Does Ron Paul have a realistic shot at winning the GOP nomination?"
Yes. Which doesn't make it a sure thing. But there will be a conservative candidate and a Rockefeller Republican. Right now, the drama is in the race for the conservative candidate, where Ron Paul shines. He isn't new, and the newcomers are getting the 'buzz' early vote, which has shifted first to Trump, then Cain and now Bachmann, but those candidates as they are vetted shed voters, as well.
Ron Paul has been vetted, will not lose the share of votes he has, and stands to gain more and more voters as people look into his record and find he is the ONLY one of the candidates who has stood for fiscal conservatism and civil liberties, for his entire career, and not just when those topics were 'fashionable'.