A prominent donor to Senator Barack Obama recently sent an e-mail plea to other supporters, asking them - for the sake of Democratic unity - to write checks to Senator Hillary Rodham Clinton to help retire her $23 million in campaign debt.

Some of the replies are unprintable, given the coarse language, the donor said. A sampling of others included:

"Why would I help pay off debts that Hillary amassed simply to keep damaging Senator Obama?"

"Gas prices are up, the markets are in turmoil, my kid's fall tuition bill is coming soon. Writing checks to politicians I don't like is not at the top of my list."

"Not a penny for that woman. Or her husband. Or - god forbid - Mark Penn," a reference to Mrs. Clinton's former senior strategist, whose firm is still owed several million dollars for work that included aggressive attacks on Mr. Obama.

As Mr. Obama and Mrs. Clinton prepare for their first joint fund-raisers to benefit the Obama campaign, in New York City on Wednesday and Thursday, their two camps are straining under the weight of continued resentments, recriminations and feelings that remain raw since the long primary battle.

Mr. Obama has asked his top donors to help raise money for her debt, and so far they have come up with less than $100,000 (though more in pledges), Clinton campaign officials said - a "paltry sum," in the words of one.

Several Obama donors said in interviews that they were balking at Mr. Obama's call for help because they believed Mrs. Clinton accumulated most of her debts after she had lost any mathematical chance of winning the nomination and was hanging on only in hopes of an Obama collapse. The idea of helping her now - and lining the pockets of Mr. Penn, a reviled figure in the Obama camp - is galling to them, they said, especially at a time when they say any available money should go to defeating Senator John McCain and the Republicans in November.

While no other presidential candidate has ever amassed so much personal and campaign debt en route to losing the nomination as has Mrs. Clinton, both Clinton and Obama donors say the larger problem for Democrats is that if the Obama camp is seen as unhelpful, Mrs. Clinton, her husband and their supporters could prove something less than a force for unity.

Among the complaints from Obama campaign officials is that Mrs. Clinton's expectation for help has been a moving target; in other words, it is unclear how much money from Obama supporters will be enough to satisfy the Clintons. Even Clinton officials and donors were at a loss to specify a number, saying only that Mrs. Clinton was helping Mr. Obama with the understanding that he would do more for her.

"There is no lack of emotion among some supporters of both candidates, but what I think the sensible elements of good will are trying to achieve is debt relief for Hillary consistent with getting Barack elected president," said Steven Rattner, a New York investment banker and leading fund-raiser for Mrs. Clinton, who is working with both camps to help Mrs. Clinton retire her debt.

The bitterness in the Clinton camp about the primary battle is well known, but several Clinton donors and campaign officials said a deeper issue remained unsettled: The belief - or, perhaps, the perception - that Mr. Obama and his aides are half-hearted in their efforts to help Mrs. Clinton and include her top donors on his leadership team.

Some of them griped that major Clinton donors were not being invited to crucial fund-raising meetings; were not being made to feel that they would receive credit for helping Mr. Obama win in November; and were not being given titles within the Obama campaign. An Obama aide said it was still early in the integration process of the two campaigns; he also added that the Obama operation was not as title-driven as the Clinton operation, which had various donors serving as "chairs," "co-chairs" and "Hillraisers."

Clinton donors and campaign officials say they remain surprised - and, among some, offended - that Mr. Obama has refused to ask his entire list of donors, more than 1.5 million people, to send $5, $10 or more to chip away at Mrs. Clinton's debt. (Obama officials said they did not want to distract their donors for the main task at hand, raising money to defeat Mr. McCain.)

"The Obama effort hasn't yielded much, but we hope it will increase," said Alan Patricof, a top Clinton fund-raiser and family friend.

"I think most people - I can't say everyone - thinks that helping Barack is the best way to get help from the Obama camp to help retire her debt, which is a major source of concern for her right now," Mr. Patricof added.

Mrs. Clinton owes an estimated $12 million to consultants and vendors, like Mr. Penn; she also lent her campaign more than $11 million. That $11 million is listed as a debt, though Mrs. Clinton has told her fund-raisers that she does not expect them or the Obama camp to repay her.

Clinton campaign officials estimated that the millions owed to Mr. Penn and his team was by far the largest part of Mrs. Clinton's debt, though they emphasized that the money was not only going for Mr. Penn's time but also for the services provided by his colleagues and his polling and strategy firm. Clinton officials said they could not provide a breakdown of those amounts.

"We're focused on the vendor debts, especially the Kinkos, the truck drivers and the small-business folks who helped us along the way," said Jonathan Mantz, the Clinton campaign's finance director.

Orin Kramer, a leading Obama fund-raiser, said he was working with other members of Mr. Obama's national finance team, like Frank Brosens and Alan Solomont, as well as Mr. Rattner, Mr. Patricof and other Clinton donors to deal with the debt issue.

The negotiations between the Clinton and Obama camps are so delicate that it is one of the issues being managed by Robert Barnett, the high-powered Washington lawyer that Mrs. Clinton asked to help structure a political relationship between them for the general election.

According to several Democrats who have spoken to Mr. Barnett, he has counseled the Clinton camp that honey will work better than vinegar in the debt talks. But Clinton donors say it is an open question whether the Clintons believe they should play hardball - signaling that they will not rally enthusiastically behind Mr. Obama unless he does more on the debt situation - or appear agreeable with the expectation that the money will ultimately come through.

A crucial test will come at the fund-raisers in New York this week, both sides said. Mr. Obama is expected to ask supporters there to help Mrs. Clinton, and Clinton donors said they were hoping for a great deal more money to come in from people heeding his call.

The New York events are on behalf of the Obama campaign, his aides said; Mrs. Clinton will not receive a cut of the take, but rather, in theory, benefit afterward from Obama donors who decide to help her. Mr. Obama and his wife have each already written checks for $2,300, the maximum donation, to Mrs. Clinton.

"Senator Obama and his staff and his supporters are working very hard on debt relief for Senator Clinton, and will continue to in any way that works best," said Bill Burton, a spokesman for the Obama campaign.