Jim writes , “The typical Republican supporter of Obama won’t be a paleo-ish antiwar conservative but a disgruntled moderate.” I don’t know about that, though I agree with most of the rest of Jim’s analysis. John McCain, despite tacking hard to the pro-war Right over the past two years, still gets a lot of support from moderates who think he’s a “maverick,” as Jim points out. Look at how many antiwar voters supported him in the N.H. primary. And the reason McCain seems to poll strongly against Hillary and Obama nationally is not because Republicans have made up ground they lost in 2006 but because moderates who abandoned the GOP as a party in 2006 have never abandoned McCain himself. That’s my eyeball impression, anyway.
So I wonder how many Obamacans there are who are not really, underneath whatever other pretenses they may put up, antiwar voters. Doug Kmiec is a good example: he came out in support of Obama  for a number of reasons that didn’t make a lot of sense. But that was because they weren’t his real reasons : he was supporting Obama apparently because of the war, and maybe out of animus against John McCain too.
In any election, there are a number of moderate or liberal Republicans who support the Democrat, just as there are usually “Democrats for Bush” or other transpartisan auxiliaries for the GOP candidate. Obama’s charisma means that he may get more of these moderate/liberal Republicans than, say, John Kerry did. But McCain is still a moderate himself, and he performed well with moderates and independents while the Republican nomination was still in contention. So I don’t believe McCain will lose that many Republican moderates or liberals to Obama, while I still think that antiwar conservatives who might have gone for Obama will now shift to Barr. This analysis mostly recapitulates Jim’s points — which actually amplify my belief that Barr and Obama are fighting for much of the same antiwar turf.
(What would be ironic, of course, would be to see the same thing happen nationally as happened in N.H. — antiwar voters going for McCain. That’s democracy…)