U.S. President Barack Obama ridiculed Republican candidate Mitt Romney on Thursday, hours after a televised debate in which the incumbent was widely seen as struggling against a resurgent challenger.

At a rally in Denver, Colorado, where the debate was held Wednesday night, Obama tried to recapture his cool campaign charm, telling supporters that he had been on stage with "this very spirited fellow who claimed to be Mitt Romney."

"But it couldn't have been Mitt Romney," Obama said, "because the real Mitt Romney has been running around the country for the last year promising 5 trillion dollars in tax cuts that favor the wealthy. The fellow onstage last night said he didn't know anything about that."

The man he debated "does not want to be held accountable for the real Mitt Romney's decisions and what he's been saying for the last year," Obama said. "So Governor Romney may dance around his positions. But if you want to be president, you owe the American people the truth."