Three predictions if McCain is the 2008 GOP nominee:
1) The media will run 24/7 stories about his age and history of health issues.
2)McCain will suddenly become a "hard-right" conservative in MSM and DNC hit pieces.
3) Military service, which was oh-so-important to the DNC when Kerry was the nominee, will become irrelevant to the MSM and the Democratic Party. It will be all about "who cares most for the children" again, like when Bubba ran against H.W. Bush and Bob Dole. And McCain will be painted as the second coming of The Grinch.
I believe that all will happen exactly as you say. I don't think McCain can be stopped. GOP voters go for established choices.