To the extent that Democrats do worse even than the economy explains, one can point to a number of factors. Given that the stimulus was inadequate — which was obvious early on — Obama could have tried to warn Americans of a long hard road ahead, and placed blame on Republicans; instead, the WH kept pretending that things were going swimmingly, never once acknowledging that the original plan wasn’t sufficient (they still haven’t). Remember the Summer of Recovery?
Worse, since the fall of 2009 the White House has systematically adopted Republican positioning on the budget; remember how the State of the Union included a freeze in domestic spending?
Policy on other fronts seemed almost designed to cede populist sentiments to the right: not even a hint of tough positioning against Wall Street, totally limp policy toward China, and more.
On the organizational side, it’s still mind-boggling how the White House deliberately shut down the whole network of grass-roots organizing that helped put Obama there in the first place. All that idealism, all that energy — and they were told to go away and let Rahm Emanuel do his deals in peace.
So again: it was mainly the economy, with the effects of a bad economy reinforced by Obama’s consistent policy of undercutting both messages and movements that might have helped Democrats weather the economic storm.