Barack Obama and Hillary Clinton embark upon a high-decibel double-act tonight, designed to silence the discordant voices that claim her supporters are bad losers or he is being less than generous in victory.

This is the Democrats' “unity week”, when the two candidates who fought each other so long for their party's nomination proclaim loudly that they are reconciled.At their first joint appearance since Mrs Clinton conceded defeat 19 days ago, she will ask her big donors gathered at the Mayflower Hotel in Washington to open their wallets — if not their hearts — to her former rival.

On Tuesday Mr Obama urged his top contributors to help Mrs Clinton to pay off a chunk of her $22.5 million (£11 million) campaign debt. Yesterday she told congressional supporters on Capitol Hill to get behind the Democratic nominee.

Tomorrow they will take the stage together at a rally in the symbolically named town of Unity, New Hampshire, where they both received 107 votes during a hard-fought January primary. On Saturday Mr Obama's supporters are inviting those who backed Mrs Clinton into their homes for “Unite for Change” parties in 3,000 locations across all 50 states.

But for all this careful choreography there have been some faltering steps. There is resentment that Mr Obama has not done more to reduce Mrs Clinton's debts, even though she has effectively written off the $12 million loaned from her own fortune.

While he hungrily eyes her small donor list - which runs into the hundreds of thousands — Mr Obama has not asked his own army of 1.4 million internet benefactors to help out Mrs Clinton. Some of his supporters say that they are disinclined to pay off debts run up in the final months of the campaign. At the same time Bill Clinton — who was in London yesterday — is said to be simmering over implied criticism of his presidency or suggestions that he played the race card in the nomination battle. He has not spoken to the Democratic nominee and this week issued only a mealy-mouthed single sentence through his spokesman, saying that he is “obviously committed to doing whatever he can and is asked to do to ensure Senator Obama is the next president”.

In public, Mr Obama has sought to be gracious to his former rival, rounding on supporters who booed mention of her name at a recent rally. “You up there!” he said, “Senator Clinton is one of the finest public servants we have in American life today!” But when Mr Obama met some of her congressional supporters, he did not show much sympathy for the red raw wounds of the vanquished, bluntly telling the likes of Diane Watson to “get over it”.

There was a similar message from Nancy Pelosi — the House Speaker who was long suspected to be a covert Obama-backer — when asked if Mrs Clinton lost because she was a woman. “I'm a victim of sexism myself all the time,” said Ms Pelosi, “and I don't spend a lot of time worrying about [it].” Mrs Clinton dutifully appeared at a short press conference alongside Ms Pelosi, emphasising that before November there would be “a lot of work for all of us” — including her husband.

She has returned to work in her Senate offices, where her staff had set up a ping-pong table during her long absence, insisting that she was not even thinking about the vice-presidency, or perhaps, not any more. Mr Obama's appointment last week of Patti Solis Doyle — sacked as Mrs Clinton's campaign manager — as chief of staff for a future vice-presidential choice, was seen as slamming the door on a so-called dream ticket.

Hold-out Clinton voters — particularly women branded the “Nobama Mamas” — are threatening to withhold their support in November. But Mr Obama believes that he can reach out in his own way to such groups and two recent polls, giving him a double-digit lead over John McCain, suggest that he is doing perfectly well without Mrs Clinton as an intermediary.

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