WASHINGTON (Reuters) - President Barack Obama has a growing lead in polls and an easier path to the White House than challenger Mitt Romney, but the Republican is still within striking distance with eight weeks to go before the election.

Obama expanded his edge over Romney after their back-to-back nominating conventions and has leads in eight of the top nine battleground states, giving him an advantage but not a lock on the race.

While bumps in the polls after a convention often do not last, Romney is running out of chances to recast the race and win over a small group of undecided voters. Three presidential debates and one vice presidential debate in October are the last major campaign events before the November 6 election.

"Clearly, heading into the final 60 days of the campaign the president has opened up an edge, and that includes in the swing states, too," pollster Peter Brown of Quinnipiac University said. "But Romney just needs to move the needle a few points and the race would be right back to even," he said.

Tracking polls by Gallup and Rasmussen gave Obama a 5-point edge on Monday. A CNN/ORC poll on Monday gave Obama a 6-point lead among likely voters, up from a tie before the Democratic convention.

The CNN poll found only three percent of likely voters were still undecided or backing another candidate aside from Obama or Romney.

The Romney camp played down the significance of Obama's gains, releasing a memo from pollster Neil Newhouse describing it as "a sugar high" and predicting economic realities would bring the race back to the tight margins that have characterized it for months.

"The basic structure of the race has not changed significantly," Newhouse said.

"The reality of the Obama economy will reassert itself."

Romney, former head of a private equity firm, has argued his business experience makes him uniquely qualified to boost job growth and turn around a stumbling economy suffering from 8.1 percent unemployment.

But he has made no headway against Obama, whose campaign spent the summer hammering Romney in advertisements as an out-of-touch millionaire whose business experience mostly involved raiding companies for cash and leaving workers jobless.

Friday's weaker than expected jobs report, released the morning after Obama concluded his convention, did not keep Obama from cracking 50 percent in the CNN poll and in his job approval rating recorded by Gallup.

'LIKEABILITY GAP'

Romney has also battled a likeability gap with Obama, and much of his convention was spent trying to paint a softer side of the former Massachusetts governor for voters who have not warmed to him.

But the CNN poll found the number of likely voters who viewed Romney favorably dropped from 50 percent before the two conventions to 48 percent. The number who viewed Obama favorably rose from 52 percent before the conventions to 57 percent.

"I think Mitt Romney's challenge is likeability," Arizona Senator John McCain told Reuters Insider in Italy.

"People are not only going to be asking themselves, ‘Are you better off than you were four years ago?' but they are going to be asking another question and that is, ‘Am I going to be better off four years from now?'" he said. "They have not yet been sold that Mitt Romney will make sure that happens."

Both camps plan to bombard swing states with television advertisements down the stretch. Republicans hope a sizable cash-on-hand advantage, $60 million in August, will help them make their case against Obama's economic leadership and convince voters a change is needed.

But Obama and his Democratic allies stayed even in the money race last month, outraising Republicans $114 million to $111 million after trailing Romney and Republicans in every month since April.

Unexpected events, like an economic meltdown in Europe or an Israeli strike against Iran's nuclear program, could still change the picture. In 2008, the financial crisis in September shifted a tight race with Republican John McCain toward Obama.

"We've still got a long way to go to the election, and we're probably going to see the race tighten up again, particularly ahead of the debates," Ipsos pollster Julia Clark said. "The key to the debates will be who is most credible on the economy."

Polls show Obama with a clear advantage on the campaign map in the battle for the 270 electoral votes needed to capture the White House.

The Real Clear Politics average of polls in nine of the key toss-up states won by Obama in 2008 showed the president leading in Colorado, Florida, Iowa, Nevada, New Hampshire, Ohio, Virginia and Wisconsin. Romney led only in North Carolina.

Those leads exceeded 3 percentage points in only three states, however - Colorado, Nevada and New Hampshire - leaving plenty of room for change.

AUTO INDUSTRY BAILOUT

Democrats have been heartened by Obama's steady lead in Ohio, a critical battleground that Romney cannot afford to lose. The Real Clear Politics average gives Obama a 2.2 point lead in Ohio, which enjoys an unemployment rate lower than the national average and where Obama's auto industry bailout is popular.

Obama also has leads in the other big battleground state, Florida, as well as the emerging swing states of Virginia and Colorado, where improving local economies and shifting demographics have helped his cause.

Romney is hoping the choice of Wisconsin Congressman Paul Ryan as his No. 2 helps him flip that state to his column. He leads in North Carolina, a historically Republican state that Obama narrowly won in 2008.

Top Romney advisers insisted they remain well-positioned to take Ohio and the White House in November. They took heart in the Republican primary race, which featured several challengers who moved past Romney in polls only to fade in the end.

"We know how to win. We are very patient," said one senior strategist. "We don't try to please everybody and understand that it's not about winning every day. Remember when Perry was 20 points ahead?"

Newhouse said Obama would eventually give up on North Carolina, where Democrats held their nominating convention last week. Obama campaign spokesman Ben Labolt called the idea "crazy."

Romney has already been preparing for the debates, which begin on October 3 in Denver with a focus on domestic policy. The vice presidential debate is October 11 in Kentucky, while Romney and Obama will meet again in a town hall format on October 16 in New York and to debate foreign policy on October 22 in Florida.

Romney began debate practice last week during the Democratic convention, sparring against Ohio Senator Rob Portman, who played Obama. Obama will sharpen his debating skills against Massachusetts Senator John Kerry.