I think the CNN Poll gives some insight into that question.
The horserace numbers are inconclusive, with Obama up a point (HRC down two): virtually meaningless, this far out. But every other number and argument cries out “Yes.”
Right now, Obama edges out McCain on the fav/unfav (HRC is way behind). And Obama’s “certainly won’t vote for” is actually five points lower than McCain’s, while his “certainly will vote for” is eight points higher.
Certainly will/unsure/certainly won’t
Hillary Clinton 37% / 19% / 43% (-6)
Barack Obama 30% / 32% / 38% (-8)
John McCain 22% / 35% / 43% (-21)
Put it a different way: to get to 50%, McCain would need to get 28/35 (80%) of the people not currently committed to voting against him.
Yes, Obama would get roughed up in a general. But so would McCain; for him, it’s time for the “tear-down” that comes after the “build-up.” (Someone really ought to republish JK Galbraith’s essay on that process.) Also, McCain is old, older than his calendar age, and might get pretty ragged before Election Day.
Anyway, a year in which there are more Democratic primary voters than Republicans in South Carolina is not a Republican year, unless something really mobilizes the Republican base or de-mobilizes parts of the Democratic base. A McCain-Obama race does neither one. Nativists and social conservatives won’t be enthusiastic about McCain, and Obama, even after being put through the meatgrinder, is just not the bogeyman HRC would be.
And that leaves out the effect of a bad recession — always bad for the party in power.
Kevin Drum just today posted a calculation from the Intrade prices showing that the betting market assigns HRC a much higher probability of being President, conditional on being the nominee, than is the case for Obama. (Those numbers moved closer together tonight, with Obama now showing about a 54%chance being elected if he’s nominated compared to about 61% for HRC.)
I’d be happy to bet on Obama if it’s Obama/McCain.