Washington, Oct 11 (IANS): President Barack Obama has conceded he had a bad night at the first debate against his Republican challenger Mitt Romney, but insisted that the "fundamentals" of the presidential race haven't changed.

"Governor Romney had a good night. I had a bad night. It's not the first time I've had a bad night," he told ABC News Wednesday as he vowed "a little more activity" at their next encounter Oct 16 in New York.

Romney, meanwhile, out to capitalise on his post debate bounce made three public appearances in the battleground state of Ohio Wednesday and plans to spend two of the next three days there.

"We can't afford four more years of Barack Obama," he said at a rally. "Ohio could well be the place that elects the next president of the United States," said Romney telling voters: "I need you to do that job. We're going to win together."

In his ABC interview Wednesday, Obama, whose supporters have wondered why he didn't raise some contentious campaign issues during the Denver debate, said those omissions from the first debate would not be game changers in the Nov 6 election.

Supporters have wondered why Obama did not press Romney over his remarks on the 47 percent of Americans being "moochers" or reliant on government support, or Bain Capital, the private equity firm he co-founded, accused of shipping jobs to China and India.

"What's important is the fundamentals of what this race is about haven't changed," he said. "Governor Romney went to a lot of trouble to try to hide what his positions are."

"One thing, maybe this is because I played a lot of sports when I was a kid and still do, if you have a bad game, you just move on," Obama said.

"You look forward to the next one. And it makes you that much more determined. The difference between this and sports is that the stakes are so high."

Meanwhile, Vice President Joe Biden and Romney's running mate Paul Ryan prepared to join battle Thursday in their lone debate with Democrats hoping to regain some ground conceded by Obama, while Republicans believe Ryan would keep their momentum going.

But A New Pew Research Centre survey found that registered voters are not that hot on Biden with 51 percent of the 90 percent who gave an opinion viewing him unfavourably as against 40 percent of the 84 percent who viewed Ryan unfavourably.

The poll also found that Republicans are more confident that Ryan will win the debate than Democrats are about Biden's chances.

However, the lower expectations could make it easier for Biden to exceed them and help reset the race in Obama's favour, analysts said.