You might think from what's going on in the national political climate that voters are getting disgusted with Barack Obama and leaving the Democratic party in droves, but that's actually not the case.
Only 13% of people who voted for Obama in 2008 now disapprove of him and only 10% of Obama voters are planning to support Republicans for Congress. Those two relatively small shifts are enough to put the President's approval rating in negative territory and to give the GOP a lead on the generic ballot.
It really doesn't take very many voters changing their loyalties to create a seismic shift in terms of number of seats lost. The GOP will make gains this year but they will likely be tenuous because just as a small number of voters turning toward them is creating the image of an onslaught this year, a small number going back toward the Democrats by 2012 could create the same image back in the other direction.
There may be a perception of a huge shift in American public opinion right now but its really a small one, albeit one that could have huge implications for control of Congress in the years ahead.