While your logic is unassailable, I think you're missing part of the dynamic to this year's race. The left wing of the Dem Party is hopping mad at eight years of Bush, and is choosing the nominee--as they chose it in 1972 and perhaps 1988. McCain is a weaker candidate than either pre-Watergate Nixon running for re-election or Vice President GHW Bush running against Dukakis. McCain resembles Bob Dole, and I think there is a fair chance Obama wins big--which he'll need to do to effect the type of "change" he's been talking about.