分析:美总统候选人辩论是"转折"

WASHINGTON — In the U.S. presidential race, a strong debate performance by Republican candidate Mitt Romney may breathe new life into his campaign to unseat President Barack Obama. Any shift in polling numbers for the two candidates may take several days to materialize.

During a contentious 90-minute encounter in Denver, Colorado a crisp-speaking and seemingly well-rehearsed Mitt Romney repeatedly attacked the president's record, Mr. Obama was often on the defensive.

The two men traded verbal jabs on federal taxes, job creation, and retiree health-care funding.

"I just do not know how the president could have come into office facing 23 million people out of work, rising unemployment, an economic crisis at the kitchen table, and spend his energy and passion for two years fighting for Obamacare instead of fighting for jobs for the American people," Romney said.

The president did fight back, but, according to many observers, he seemed to lack the same zeal people observed from the debates four years ago.

"Over the last 30 months, we have seen five million jobs in the private sector created," said Obama.

Political analyst Charlie Cook says President Obama's performance fell short of the public's expectations, while Mitt Romney's exceeded them.

"By any standard, he [Romney] did very, very well. Obama seemed to be like a team sitting on a lead," Cook noted.

Public-opinion polls have shown Mitt Romney with higher unfavorable than favorable ratings by voters. That may now change, according to Republican pollster Glen Bolger.

"Romney came across as somebody who is more genuine than they had realized, and also as somebody who also they could see stepping into the Oval Office," Bolger noted.

Polls show a tiny fraction of the electorate undecided on how they intend to vote in November, so the effect of the debate is hard to predict, according to Charlie Cook.

"No question Romney won the debate," said Cook. "The question is, how much does this change things? And I think in terms of national polls, no question he [Romney] is going to get a few points out of this. But the harder points and the more relevant points: does he move Ohio, and does he move these swing voters in these swing states?

The two candidates face each other in two more debates later this month.