Andrew Gelman uses an old paper to size up the 2010 elections:
The current state of the generic polls gives the Democrats .412/(.412+.377) = 52% of the two-party vote. Going to the graph, we see, first, that 52% for the Democrats is near historic lows (comparable to 1946, 1994, and 1998) and that the expected Democratic vote–given that their party holds the White House–is around -3%, or a 53-47 popular vote win for the Republicans. Would 53% of the popular vote be enough for the Republicans to win a House majority? A quick look, based on my analysis with John Kastellec and Jamie Chandler of seats and votes in Congress, suggests yes.
The Dish 