WASHINGTON (Reuters) - After several difficult weeks, Republican Mitt Romney found his footing on Wednesday night in a strong debate performance against Democratic President Barack Obama. The question is whether it is too late to make a difference.

Romney could see a burst of fundraising, new interest from undecided voters and a wave of support from his fellow Republicans after he appeared to have emerged as a clear victor in his first face-to-face confrontation with Obama. Romney likely will benefit from favorable news coverage as well.

Still, with the November 6 election little more than a month away, Romney is running out of time to seize the lead.

Voting has begun in some form or another in 35 states, and 6 percent of those have already cast their ballots, according to a Reuters/IPSOS poll released on Wednesday.

And while debates are among the most memorable events of any presidential campaign, there is little evidence that they can change the outcome of an election.

Obama may have underwhelmed, but he avoided the sort of disastrous performance that can cause backers to reassess their support.

"Nobody is going to switch sides on the basis of this debate," said Samuel Popkin, a political science professor at the University of California at San Diego.

Standing on the same stage as the president for the first time, Romney took full advantage of the opportunity to convince voters that he is up to the task of leading the nation.

Speaking in crisp, bullet-pointed paragraphs, Romney came armed with a quiver of "zingers" built for a long afterlife on cable television and YouTube.

"You're entitled to your own house and your own airplane, but not your own facts," Romney told Obama at one point.

Obama, by contrast, looked unhappy to be on stage.

His answers were meandering and professorial, laden with facts but short on vision. He argued that Romney's tax and budget plans don't add up, but he steered clear of other lines of attack that have proven effective.

"Romney won. The real surprise is that he won so clearly," said Paul Sracic, a political science professor at Youngstown State University.

Voters seemed to agree.

Some 67 percent of those surveyed by CNN in a "flash poll" after the debate declared Romney the winner. Obama's re-election prospects on Intrade, an online prediction market, fell from 74 percent to 66 percent.

Obama maintains an advantage in opinion polls. On Wednesday, he led Romney by 47 percent to 41 percent in the daily Reuters/IPSOS tracking poll, a margin that has held fairly steady since the middle of September.

Other polls have shown the race to be a little closer. Obama holds clear leads in most of the politically divided states that are likely to decide the election.

DEBATES HAVEN'T HAD MUCH OF AN IMPACT

Many pollsters expect Obama's margin to shrink somewhat over the coming month, but debates rarely have much of an impact.

Opinion polls have shifted by an average of less than 1 percent in the wake of the 16 presidential debates that have taken place since 1988, according to research by Tom Holbrook, a political science professor at the University of Wisconsin at Milwaukee.

The biggest shift came in 2004, when Democratic challenger John Kerry gained 2.3 percent points on Republican President George W. Bush. Bush won the election.

People who have made up their minds to vote against Romney won't change their minds no matter how presidential he looks in debates, said Popkin, author of "The Candidate: What it Takes to Win - And Hold - the White House."

"If you think he's a selfish person who's out for the rich, you can still think he's a confident, comfortable, genial executive who fires you with a smile," he said.

And some voters may have been actually focusing on the words the two candidates said, rather than the manner in which they said them.

While Romney played down his conservative positions in an effort to reach out to centrist voters, Obama successfully emphasized themes like education and deficit reduction that appeal to this group, several observers said. His new emphasis on expanding opportunity, rather than ensuring fairness, also could help among the more ideologically moderate voters who have yet to make up their minds.

"Often voters are looking more for substance than for style," said Dotty Lynch, a professor of communication at American University.