Bill and Hillary Clinton have made their first joint campaign stop in support of Democrat Barack Obama's bid for the US presidency.
The appearance of the former first couple in Scranton, Pennsylvania, is seen as an attempt to boost Mr Obama's vote in the US blue-collar heartland.
Mr Obama's Republican opponent, John McCain, will try to revive flagging poll ratings in a key state, Virginia.
He has signalled a change in tactics after some harsh attacks on Mr Obama.
But he nevertheless said he would "whip" Mr Obama's "you know what" in t= he final TV debate between the two candidates, to be held on Wednesday.
Both presidential candidates are preparing to unveil major new plans to deal with the current financial crisis and the flagging US economy.
Aides to Mr McCain say the Republican will unveil a new economic strategy expected to include tax cuts.
Mr Obama is scheduled to give a "major policy address" in the swing state of Ohio, his campaign said, to outline an "economic rescue plan for the middle class".
Election 'too important'
The Clintons joined vice-presidential candidate Joe Biden in his birthplace, the town of Scranton, Pennsylvania, to call on voters to make Mr Obama president.
This was their first campaign appearance together since Mr Obama narrowly defeated Mrs Clinton in the Democratic primaries earlier this year.
"This election is too important to sit on the sidelines of history," said Mrs Clinton, who defeated Mr Obama in the Pennsylvania primary by 10 percentage points.
"It took a Democratic president to clean up after the last President Bush, it's going to take a Democratic president to clean up after this President Bush," she added.
"Make no mistake about it. We've done it before and we'll do it again. America will once again rise from the ashes of the Bushes."
Bill Clinton asked Hillary's supporters to throw their weight behind Mr Obama.
"You need to remember, if you supported her, why you did it," he said.
"If you ask yourselves who has the best ideas, who's got the best instinct, who's got the best ability to understand these challenges, who's got the best supporting cast, the answer is Barack Obama."
'Beyond the pale'
Meanwhile Mr McCain's team said he would change tack after a series of personal attacks on his opponent, and the candidate himself called for a "respectful" campaign.
Over the weekend, the Republican candidate became embroiled in a war of words with racial undertones after clashing with a civil rights icon.
John Lewis accused Mr McCain's campaign of "sowing hatred" against his opponent and said he had been reminded of 1960s segregationist George Wallace.
Mr McCain, who recently said Mr Lewis was one of his most admired Americans, called the reference "beyond the pale".
Mr McCain has also tried to cool his supporters' resentment of Mr Obama, for which he won praise from his opponent.
In Minnesota on Friday, Mr McCain defended Mr Obama after some at the town hall meeting labelled him a "terrorist", "an Arab", a "traitor" and a candidate who inspired fear.