The financial crisis of 2008 made it inevitable that unemployment would rise sharply through 2009. It also caused the budget deficit to skyrocket:

Most voters, of course, don't follow these issues closely enough to gain a detailed understanding of cause and effect. They just tend to notice that unemployment and the budget deficit have risen while President Obama has held office.

Republicans have worked assiduously to blame these conditions on Obama's policies even though they were obviously caused by conditions he inherited. At the same time, they have worked relentlessly to create a social stigma around his efforts to push back. The result of this campaign can be seen in things like Politico's weekend article chastising Obama for blaming his predecessor:

President Barack Obama is trying to ride the wave of anti-incumbency by taking on an unpopular politician steeped in the partisan ways of Washington.

It doesn’t matter that George W. Bush left office 16 months ago.

The White House’s mid-term election strategy is becoming clear – pit the Democrats of 2010 against the Republicans circa 2006, 2008 and 2009, including Bush.

It’s a lot to ask an angry, finicky electorate to sort out. And even if Obama can rightfully make the case that the economy took a turn for the worse under Bush's watch, he's already made it - in 2008 and repeatedly in 2009.

It’s not clear that voters still want to hear it.

The story quotes ten sources commenting on Obama's occassional habit of faulting the Bush administration. Of the ten, eight criticize Obama.