Right now the Democrats have a soid advantage throughout the Midwest, the Northeast, the West Coast, the Southwest, and some of the Southern border states. In fact, when you look at a region like the Northeast, the Democrats control literally all of New England and all but three seats of New York (out of 29).
This makes sense, as the coastal areas are the Democratic base. However, there isn't nearly the same level of uniformity of Republicanness in the South. Partly, that's due to large populations of Black folks that vote Democrat, but there are still a fair amount of moderate white Southerners in the House. I suspect that social democracy won't sit well with these folks, and some of them (like Jim Marshall of Georgia, for example) will lose their seats if the Republicans make a point of resisting Obama's liberal agenda.
Now, I don't really think that this is a bad thing. It's just part of the cost of doing business, and I suspect that Democrats will win back Bill Jefferson's seat in Louisiana and gain Jim Gerlach's seat in Pennsylvania, for starters. But I would imagine that the GOP would pick up some ground in their base region.
However, the Senate is a bit different, and I think it looks likely that, unless the Democrats are a total disaster, they ought to pick up a few seats there. But I'd guess the Republicans win about 10 or so seats in the House, and that this would "prove" their strategy of returning to conservative principles. This would lead to a recurrence of the "one last heave" strategy (see Smith, John, of the British Labour Party) and someone like Sarah Palin gets the nomination and can't attract any voters outside the base.
It seems to me that the GOP needs not to secure its base, but rather to broaden its base. I do think that Black voters are a promising avenue for the GOP to pursue--they're culturally and socially conservative, for one, and a populist Republican like Huckabee might be able to peel them off. Would that be enough? I don't know. Then again, if history is any guide, an increase in Blacks voting Republican in the South would lead to an increase of Southern Whites voting Democrat, so back to the drawing board for the Repubs, I guess...
