President Barack Obama settled into a Virginia resort Saturday, plotting to transform his pitch to voters after a lackluster first clash with Mitt Romney dampened his re-election hopes.

The Republican nominee, fresh from slating Obama over the attack on the US consulate in Benghazi, opened another foreign policy row, over China, accusing the president of standing by while "cheating" Beijing manipulates its currency.

Shell-shocked Democrats want a more feisty and dynamic Obama to show up at the second debate at Hofstra University in New York on Tuesday, after the president's meek effort 10 days ago sent his poll numbers tumbling.

To prepare, the president planned four days of cramming at the picturesque Kingsmill golf resort outside the historic colonial town of Williamsburg in the heart of Virginia, a state that could help Obama claim a second White House term.

Twenty-five days before the November 6 election, Obama huddled with senior aides and was taking on Senator John Kerry, who is playing Romney, in a series of mock debates.

His campaign promised a rethink after Obama was comprehensively outmaneuvered by Romney in Denver, and he will likely be more proactive Tuesday in countering what he has called his opponent's "extreme" political makeover.

Vice President Joe Biden prosecuted a more forensic attack on Romney when he met the Republican vice presidential nominee, Paul Ryan, in their debate on Thursday, a showing that cheered Democrats dismayed by Obama's performance.

Romney, who Friday said his campaign was reaching a "crescendo of enthusiasm" was campaigning in Ohio Saturday for the fourth time in five days, in a concentrated blitz of the state.

He chose the state, which has seen an exodus of blue collar jobs to low wage economies abroad, to hammer the administration's decision to put off an assessment of China's currency policy until after G20 meetings next month.

"Over the past several years the president has failed to call China a currency manipulator," Romney said.

"He had the occasion on Friday to come out with that official designation. You know what they said? 'We're not going to make any determination until after the election.'"

"Let me tell you, on day one of my administration I will label China a currency manipulator."

With Obama off the road, his campaign is trying to protect its flank in Ohio, and announced on Saturday that rock legend Bruce Springsteen would join former Democratic president Bill Clinton to campaign in the state next week.

The Boss, who drummed up huge crowds for Kerry when he was running for president in 2004, will also appear on his own on the same day for Obama in Ames, Iowa.

In a colorful intervention in the campaign on Saturday, media mogul Rupert Murdoch accused Biden of lying about the administration's relationship with Israeli leader Benjamin Netanyahu.

"Nightmare for Israel if Obama wins. Biden outright lied about personal relations with Bibi," Murdoch wrote on Twitter.

Murdoch also weighed in on the administration's shifting story about the attack in Benghazi that killed US ambassador Chris Stevens and three other Americans, a day after Romney launched his own attack on the issue.

"White House still lying about Benghazi. HAD to know truth, or is whole admin a shambles? Biden threw CIA under bus, now WH throws State!" the News Corporation supremo wrote.

Obama has seen Romney take the lead in national polls and eat deep into his prior advantage in battleground state surveys since the Republican's clear victory in the Denver debate 10 days ago.

An average of polls conducted by the RealClearPolitics website gave Romney a 1.3 percent lead nationwide Saturday, and showed him winning in swing states Florida, North Carolina and Colorado.

The president retains narrow leads in Ohio, Virginia and Iowa, but polls in those states since the first presidential debate have shown clear movement towards the Republican.

The Romney campaign is also increasingly confident about Ohio, which Democrats see as a firewall for Obama, and which has been decisive in numerous US elections.

Obama chose Saturday to highlight the auto industry bailout he championed, and which Romney opposed, in an apparent message to Ohio, where one in eight workers are employed in the sector.

"Today, auto sales are the highest they've been in more than four years," Obama said in his weekly radio and Internet address.

"GM is back," he continued. "Ford and Chrysler are growing again. Together, our auto industry has created nearly a quarter of a million new jobs right here in America."