Nate Silver's two cents:
Democrats — if they are expecting to do better in 2012 than they did this time around — might actually be pleased that elections have become so strongly aligned to partisan orientation. They now have just 12 seats in which Mr. Obama won a minority of the vote to defend — whereas Republicans have 55 where he took the the majority instead. So if there is even a fairly modest shift back to Democrats in 2012, and the shift is again fairly uniform, they could be in a position to achieve quite a few gains.
Or, if the economy improves and — having facilitated a more even balance of power in Washington — the electorate becomes somewhat less angsty, the incumbent advantage could become stronger again, and the gains that Republicans made could prove to be relatively “sticky” — as they were, for instance, after 1994.
The Dish 