We're reasonably sure you haven't heard this argument yet. Some say it was the economy that sank the Democrats. Some say it was poor communication. Others think it was the health care bill. Michael Bérubé thinks it was Obama's 2009 Diwali celebration.
At Crooked Timber, Bérubé argues that, in "this chanting-and-smirking festival from last fall," the "roots of the debacle" of Election Day 2010 are evident. He provides a video clip:
"Nothing, I think," comments Bérubé, "can encapsulate Obama’s arrogance, or his profound alienation from ordinary Americans." He thinks it was the White House's realization of its "colossal error in judgment ( ... noting with alarm that overnight, 16 percent of Americans suddenly came to believe that Obama is Hindu)" that led to the Diwali 2010 celebration being pushed back to "just after the midterm elections."