Republican Sarah Palin and Democrat Joe Biden clashed on the economy and Iraq during a lively but polite debate on Thursday, and aimed the most criticism at their rivals at the top of the ticket.

In the only vice presidential debate ahead of the Nov 4 US election, Biden accused Republican presidential contender John McCain of being out of touch on the economic crisis and dismissed his claim to be a "maverick" on crucial issues facing Americans.

Palin said Democratic White House candidate Barack Obama was too partisan to work across party lines to accomplish change and was waving a "white flag of surrender" in Iraq.

Both camps claimed victory in a debate unlikely to dramatically change a White House race that Obama leads. Two polls taken after the debate, by CNN and CBS News, judged Biden the winner, but the CNN poll found a big majority thought Palin did better than expected.

With all eyes on Palin in her national debut in an unscripted format, the 44-year-old Alaska governor turned in a steady and aggressive performance in which she repeatedly attacked Obama and pledged she and McCain would work for the middle-class.

She frequently displayed the folksy style that has become a favorite target of late-night comics. "Aw, say it ain't so, Joe," she told Biden at one point, adding a "doggone it" for good measure.

Biden, 65, a veteran foreign policy expert, had one emotional moment, choking up when recalling having to raise his two young sons alone after their mother died in a car crash.

As the two strode on the stage, Palin greeted Biden, saying: "Nice to meet you. Can I call you Joe?"    

The debate came as new polls show Obama has solidified his national lead and gained an edge in crucial battleground states as the Wall Street crisis focuses the attention of voters on the economy.

McCain and Obama reclaim the campaign spotlight on Tuesday when they meet in their second presidential debate in Nashville, Tennessee. Both candidates watched the debate from the campaign trail -- Obama in Michigan and McCain in Colorado.

Biden and Palin both said they would work to change current US economic policy to make it more friendly to middle-class workers, but Biden noted McCain had called the fundamentals of the economy strong as the Wall Street crisis broke out.

"That doesn't make John McCain a bad guy, but it does point out he's out of touch," Biden, a Delaware senator, said in the debate on the campus of Washington University in St. Louis, Missouri.

Palin said McCain had been talking about the American workforce and said Obama would raise taxes on American workers and small business owners. Obama in fact has called for a middle-class tax cut and would raise taxes only on those making more than $250,000.

"I do respect your years in the US Senate, but I think Americans are craving something new and different," Palin told Biden.

Biden pledged he and Obama would end the war. Obama is an early critic of the Iraq war who has called for a 16-month timeline to withdraw US troops. "Your plan is a white flag of surrender," Palin told Biden.

The highly anticipated match-up promised more than the usual drama because of curiosity about Palin, a relative unknown who was thrust into instant celebrity when she was selected as McCain's No. 2 in August.

The encounter may have drawn a larger television audience than the 52 million who watched last week's first debate between the presidential candidates.

Biden said the $700 billion bailout of Wall Street he voted for, along with Obama and McCain, might force the Democrats to reconsider their promise to double foreign aid.

"The one thing we might have to slow down is a commitment we made to double foreign assistance," he said when asked what programs might have to be jettisoned because of the financial crisis.

Palin said there was nothin