WASHINGTON - MR Barack Obama and Mrs Hillary Clinton have put on a convincing show of personal amity, but political calculations are not far behind as the Democrats join forces in the battle for the White House.

If former president Bill Clinton still nurses grievances from this year's bruising primary epic, and a dwindling band of his wife's supporters are threatening to vote for Republican John McCain, Mrs Clinton at least has moved on.

'I don't see any divergence of interests. She needs to do everything she can to get Senator Obama elected president, and be seen doing everything she can,' said Mr William Galston, a former adviser to Mr Clinton.

The two senators staged their first joint campaign rally in the aptly named New Hampshire town of Unity on Friday. Both spoke passionately of their desire for unity to end Republican rule for the sake of a nation ardent for change.

But they still face tricky questions over what role Mrs Clinton will take in the Obama campaign and at the Democrats' August convention in Denver - and, eventually, what job she might solicit in an Obama administration.

According to a New York Times report last week, Mrs Clinton has enlisted the help of high-powered Washington lawyer Robert Barnett to broker those issues, and also to get help to repay her whopping campaign debts.

Mr Clinton is said still to be smarting over being portrayed as a closet racist by some Obama supporters during the primary campaign, and is taking his wife's agonising loss personally.

The former president, still a star draw for many in the party, has given only tepid backing to Mr Obama. But both he and his wife on Friday each donated the maximum legal limit of US$2,300 (S$3,135) to the Obama campaign, aides said.

That financial gesture of reconciliation came after Mr Obama gave the same amount to help retire the former first lady's campaign debts of US$22.5 million.

His donation came at an elite gathering late on Thursday of top Clinton fundraisers, where the two senators rolled out their unity show before heading to the New Hampshire town where they split the primary vote exactly in January.

Most of those in attendance appeared eager to take the fight to the Republicans on Mr Obama's behalf, although one guest told ABC the event at Washington's historic Mayflower Hotel felt like a 'dentist's appointment.'

Mr Obama has been reaching out by hiring Mrs Clinton campaign staffers, most of whom will be out of a job this month. Mr Neera Tanden, Mrs Clinton's former campaign policy director, is the latest to join, as his domestic policy director.

Opinion polls meanwhile suggest that disaffected Clinton voters are returning to the Democratic fold. The proportion that was threatening to vote for Mr McCain rather than Mr Obama was as high as one-third a month ago.

But now only 11 per cent of Clinton supporters still plan to defect to Mr McCain, according to a Los Angeles Times/Bloomberg poll released on Tuesday.

Recent polls also suggest little appetite for Mrs Clinton to run as Mr Obama's vice presidential nominee, despite persistent demands for that 'dream ticket' from some of her supporters.

Clear majorities of independent voters in four battleground states where Mr Obama is now beating Mr McCain - Colorado, Michigan, Minnesota and Wisconsin - are against the idea, according to the Quinnipiac University Polling Institute.

For those all-important swing voters, Mrs Clinton as running mate would be 'a liability for Obama, not an asset,' said the institute's assistant director, Peter Brown.

Political scientist Eric Davis of Middlebury College in Vermont said Mrs Clinton's female supporters were mostly on-side with Mr Obama, as awareness grows of Mr McCain's anti-abortion voting record and his free-market economic policies.

'The white men she got in Ohio, Pennsylvania, states like that, they seem less willing to support Mr Obama,' he said.

'If she can help get some of those people to vote for Obama rather than McCain, that's probably the most important thing she could do.' -- AFP