The US presidential election moved into high gear on Monday as two new opinion polls showed Republican John McCain taking the lead over Democratic rival Barack Obama.
McCain, a decorated war hero who based much of his early campaign on the strength of his experience, wrestled last week for Obama's mantle of change with the help of his surprise vice presidential pick Sarah Palin.
A USA Today/Gallup survey showed McCain ahead of Obama 50 per cent to 46 per cent among registered voters, a turnaround from a previous poll taken by the newspaper just before last week's Republican National Convention.
That poll had McCain trailing Obama by seven percentage points.
A new Gallup daily tracking poll found McCain had moved into a 48 to 45 per cent lead ahead of the November 4 election -- his best performance since May.
Experts attributed the McCain rebound to his party's convention and the surprise naming of Alaska governor Palin.
"He's in a far better position than his people imagined he would be in at this point," political scientist Larry Sabato of the University of Virginia was quoted by USA Today as saying.
McCain and Palin vowed to use their history of fighting corruption to shake up Washington at a series of campaign stops after the Republican National Convention.
"In politics, there are some candidates who use change to promote their careers, and then there are those like John McCain, who use their careers to promote change," Palin told cheering crowds in Wisconsin.
"We're going to win this election and let me offer a little advance warning to the old big spending, do-nothing me-first country second Washington crowd: change is coming. Change is coming," McCain said the next day in Colorado.
Obama ridiculed McCain's promise of change and hammered the Arizona senator on the limping US economy, saying the Republican represented no change from Bush.
"John McCain, who is a good man and has a compelling biography, has embraced and adopted the George Bush economic platform," Obama said on ABC television.
The Illinois senator argued that voters would realize that the election was a choice between a new direction and discredited Republican policies.
"If they like what they've had over the last eight years, then they'll go with McCain. And if they don't like it, hopefully they'll go with me," he said.
Obama's running mate Senator Joseph Biden called McCain's commitment to change "malarkey."
"Tell me one single thing they're going to do on the economy, foreign policy, taxes, that is going to be change," Biden said on NBC.
The Democrats have had a hard time targeting Palin, who is popular among conservatives and has garnered public sympathy in the wake of the media's response to news that her 17-year-old daughter was pregnant and planned to keep the baby.
Senator Hillary Clinton, who narrowly lost the Democratic primary and was incredibly popular among white women, has refused to criticize Palin even though the McCain campaign has actively targeted her disgruntled supporters.
Clinton, who has kept a low profile since she dramatically ceded to Obama at the Democratic National Convention in August, is expected to attack McCain at three events in Florida Monday.
McCain has been sharp in his criticism of Obama, warning Sunday that his rival did not have good "judgment" or a record of challenging his own party's dogma.
"He never took on his party on a single major issue, I have taken them on a lot," McCain said on CBS.
"I think I can make a strong case that whatever the issue, he doesn't have the judgment."
Neither headliners held rallies Sunday although McCain and Palin introduced themselves to voters at a Mexican restaurant in New Mexico and a barbecue joint in Missouri and Biden spoke at a Montana high school.
The Republican candidates had a rally planned in Missouri and a fundraising dinner in Obama's hometown of Chicago on Monday. Obama had two rallies planned in Michigan on Monday and another in Virginia on Tuesday. Biden was due to be in Wisconsin and Iowa on Monday.