Biden speech leads campaign fight for Obama

Vice President Joe Biden on Thursday assumed the role of top campaign surrogate for President Barack Obama, harshly criticizing the economic policies of Republican presidential contenders Mitt Romney, Newt Gingrich and Rick Santorum as a threat to the American middle class.

"If you give any one of these guys the keys to the White House, they will bankrupt the middle class once again," Biden told autoworkers in Ohio, a key battleground state for Obama's re-election bid in November.

The speech at a United Auto Workers hall in Toledo was the first of four planned in coming weeks by the vice president. It came hours before the Thursday night release of a 17-minute documentary that frames the narrative of the Obama presidency.