McCain's problem is that to get elected "big time" he needs votes from people outside of Arizona. And he has to start by getting a lot of republican votes... unless he really thinks an independent can win.... and he doesn't think that.
He's not getting mine. Ever. Even if he is the GOP nominee.
See, I think McCain already knows that he can't win as a Republican. He's been down that road before. I think he changes parties and runs, betting that enough centrist Dems and RINOs are out there to give him the WH.