"I got this," Obama said in a radio interview and predicted that Democratic "hand wringing" over his limp debate showing, which precipitated a polling slump, would be a mere memory after his next clash with Romney on Tuesday.
Obama's campaign team meanwhile launched a new assault on the resurgent Republican nominee, 26 days before the election, accusing him of hiding "extreme" stances to win support in the vital political center ground.
Democrats were mystified by Obama's peevish, lethargic and muted effort in Denver last week, and watched Romney's subsequent surge into the lead in national polls and comeback in several state battlegrounds with alarm.
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"At the debate, I think it is fair to say, I was too polite," said Obama in an interview broadcast on the Tom Joyner radio show on Wednesday.
"It is hard to sometimes keep on saying, 'What you're saying isn't true,' it gets repetitive. The good news is, that it's just the first one."
But Obama, famous for his no-drama persona, rebuked supporters who had begun to see his re-election bid as a "cakewalk," saying the race was always going to be close, and his prior lead was a result of Romney's repeated mistakes.
"This is a long haul... as long as folks stay focused, we will win this thing," Obama said, after Joyner told the president some supporters were "scared to death."
"By next week I think a lot of the hand wringing will be complete because we are going to go ahead and win this thing," the president said.
With Obama back at the White House, Romney had the campaign trail to himself and planned to squeeze in three events in Ohio, again shaping up as the epicenter of the White House race.
The state has lost thousands of blue collar jobs abroad, so Romney was on fertile political ground as he warned China's economy was gaining fast on America, but promised US manufacturers can compete if fair trade is restored.
The former corporate buyout specialist accused Obama of "laxity" on enforcing free trade rules and warned he would not allow China to keep taking US jobs.
Obama's campaign accused Romney of peddling "head-spinning falsehoods" and suggested he had swelled his fortune by investing in Chinese firms guilty of pirating US intellectual copyright.
Democrats also tried to snare Romney in a culture war minefield, after he told the Des Moines Register newspaper in Iowa that he would not introduce any legislation as president restricting the right to abortion.
Since Romney has said he would appoint Supreme Court judges who opposed the procedure and would prevent US aid funds being used to help overseas agencies that provide abortion services, Obama's team scented a cover-up.
"We know that the real Mitt Romney will say anything to win... he is cynically hiding his positions," said Obama's deputy campaign manager Stephanie Cutter.
"Governor Romney has been dishonest about his plans on issue after issue, he is trying to close the deal just like he did in the board room.
Romney later suggested his statements were not contradictory because he would use the presidency's executive powers, not write a bill, to halt government funds for foreign organizations that promote abortion.
"I think I've said time and again. I'm a pro-life candidate. I'll be a pro-life president," he said.
The Obama camp sees the abortion comments as a way to dent Romney's standing among women voters. Several polls show he improved among the crucial demographic after last week's first of a trio of debates with Obama.
Presidential candidates frequently tack to the political center ground to appeal to moderate voters once they have solidified support in their own party base after winning their nominating contests.
But for Romney, who struggled to cement support among conservatives earlier this year, the process has come late, and was not truly under way until his performance in the debate in Denver.
He has also tried to moderate his positions on issues including taxation for the rich, immigration and health care as well as on abortion.
Attention is turning to Vice President Joe Biden's attempt to turn the tide for his boss in his debate clash on Thursday night in Kentucky with Republican vice presidential nominee Paul Ryan.
Obama predicted Biden would be "terrific" and Romney said Ryan would "do great."
New polling Tuesday showed an unsettled race.
Some national polls -- like Gallup's daily tracking survey which had Romney and Obama tied at 48 percent -- suggested Romney's debate bounce was subsiding.
But there was movement towards Romney in state surveys that had the race in battlegrounds like Nevada, Florida, Nevada and Ohio within a few points.
