BARACK Obama has demanded truth from the "real Mitt Romney" as aides promised a "hard look" at strategy after the US president's listless performance in the first White House debate.
Passionate, cutting and engaged, in stark comparison to his debate showing, Obama told 12,000 cheering supporters at a chilly lakeside rally in Denver that the Romney who turned up to their first head-to-head clash on Wednesday night was an impostor who had covered up unpopular positions.
"I met this very spirited fellow who claimed to be Mitt Romney," Obama said.
"It couldn't have been Mitt Romney because the real Mitt Romney has been running around the country for the last year, promising $5 trillion in tax cuts for the wealthy.
"The fellow on stage last night said he didn't know anything aboutpoking fun at Romney's complex offshore tax arrangements, which Democrats highlight to press the case he is indifferent to middle-class struggles.
About 40 million people watched Wednesday night's debate on television, according to preliminary figures by the Nielsen TV ratings service.
Romney basked in the plaudits for his performance as he addressed a fundraising event in Colorado before flying to Virginia, saying Americans had seen two contrasting visions for the future on stage in Denver.
The Republican challenger made a surprise appearance at the Conservative Political Action Conference, thrilling hundreds of attendees as he stepped on stage to join his sons who were scheduled guests.
"I know this is going to be a close-fought battle," Romney said.
"We need to win Colorado. You know what, if we do, we are going to win