McCain cannot be separated from either McCain Feingold or or his vociferous Illegal alien push. Illegals is a hot enough button that the five front runners - including Fred are tainted - Fred less than the other four. Politics abhors a vacuum. The second tier hopefuls will move up, if only due to obscurity.
And the possibility is very real that liberals could see more gain in crossing over and voting for Ron Paul than in the choices offered by their own primaries. I myself did that when the Goracle was posing as a pro 2nd amendment centrist, against Dukakis in '88.
I have been watching politics for a long time, and this is as changeable a lineup as I can ever remember.
He is popular only among anti-war isolationist, very few of which are found within the Party he is seeking nomination.
He will bolt for the Constitution Party by mid February, unless he just wants to play spoiler to the RNC nomination process, guaranteeing Rudy or Romney the nomination.