Barack Obama has gone back on the attack against Republican rival Mitt Romney as the president's campaign team vowed to learn lessons from his muted performance in the first presidential debate.
Speaking to a rally of about 12,000 people, Mr Obama accused the former Massachusetts governor of being untruthful during the 90-minute debate in Denver.
"When I got onto the stage, I met this very spirited fellow who claimed to be Mitt Romney," he said.
"But 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 that favour the wealthy. The fellow on stage last night said he didn't know anything about that.
"If you want to be president, you owe the American people the truth."
Mr Romney, who appeared confident and relaxed during the debate, basked in the plaudits for his performance as he addressed a fundraising event in Colorado before flying to Virginia.
He told hundreds of delegates at the Conservative Political Action Conference that Americans had seen two contrasting visions for the future on stage in Denver.
"I saw the president's vision as trickle-down government and I don't think that's what America believes in," Romney said. "I see instead a prosperity that comes through freedom."
The Republican presidential hopeful, who has been trailing in key states, had needed a good performance in the first of the three debates after a number of missteps,such as comments disparaging 47% of Americans as being dependent on the government and his response to attacks on a US compound in Libya.
And polls taken after the face-off showed he had gained some ground on his rival.
According to a Reuters/Ipsos poll, Romney is now viewed positively by 51% of voters, the first time he has enjoyed a net positive in the race. Obama's favorability rating remained unchanged at 56%.
Voters now see Mr Romney as a better bet to boost the economy, spur job creation and manage the budget deficit, the poll suggested.
He also narrowed Mr Obama's advantage on taxes, the Social Security retirement programme and the Medicare health insurance programme for the elderly and disabled.
The President, however, appeared to suffer little damage with 54% of people surveyed saying their opinion of him had not changed, while 16% said their opinion had improved and 18% said they viewed him more negatively.
Obama's campaign has conceded that the incumbent must be sharper in countering his opponent and crisper in explaining his ideas to the American people.
"We are going to take a hard look at this," Strategist David Axelrod said. "I'm sure we will make adjustments."
More than 67 million Americans watched the debate on television, a 28% increase on the 52.4 million who saw Mr Obama take on John McCain in the first debate in 2008.
The next two debates are October 16 in New York and October 22 in Florida.
Vice President Joe Biden and Romney's running mate, congressman Paul Ryan, will also face each other on October 11 in Kentucky.