President Biden’s top campaign brass on Monday tried to tamp down the panic that had captured his financial base in the campaign’s most formal outreach yet to its wealthiest supporters after last week’s damaging debate.

In a Zoom audio call on Monday with about 500 members of the campaign’s National Finance Committee and some other contributors, some of the Biden campaign’s most senior officials, including the chair Jen O’Malley Dillon, the deputy campaign manager Quentin Fulks and the pollster Molly Murphy, presided for an hour.

“Everyone just needs to breathe through the nose for minute,” Chris Korge, the finance chair of the Democratic National Committee, said toward the end of the call. The New York Times was connected to the call by an authorized participant.

The senior Biden officials downplayed the political fallout of the debate, held on Thursday in Atlanta, but provided precious little new information to the members of the National Finance Committee. Those financiers have been locked in a ceaseless, rolling conversation with their own networks on conference calls and Signal threads since Thursday night about whether their investment in the Biden campaign has been the right decision.

The remarks Monday did little to stem the anxiety of the campaign’s well-heeled patrons, according to people on the call who described it while it was still ongoing. Rufus Gifford, a finance chair for Mr. Biden, did say that fund-raising numbers in June would be “extremely strong.”

The Biden campaign took no live questions from donors; instead, contributors submitted queries through the Zoom messaging app, but other attendees could not read them, according to people on the call. The campaign then chose among the presubmitted inquiries. The campaign manager, Julie Chavez Rodriguez, did not join the call.

Some of those in attendance it described it as almost facile and rudimentary.

One donor asked the campaign how it would respond to a significant erosion of polling; the campaign largely dismissed the concern. “The media has spent a ton of time blowing this out of proportion,” said Mr. Fulks, the deputy campaign manager. “We are not going to be in a defensive posture on this campaign.”

“I want to reiterate, without sounding Pollyannish or sounding defensive at all, is that at the end of the day the one thing that we are not going to do is win this race by continuing to talk about Joe Biden’s age,” Mr. Fulks said at another point. “We are here talking to you all because we know that we have to address it.”

Ms. O’Malley Dillon, the campaign chair, conceded that the debate “did not go exactly as we had hoped and exactly as the president had hoped.” Ms. Murphy, the campaign’s senior-most pollster, said internal surveys suggested that voters had not shifted. “Voters saw the debate, they took it in and didn’t change their minds,” she said.

Despite the tightly controlled format of the call, the first question the Biden team chose to answer was about Mr. Biden’s fitness to serve.

“He knows he has to get out there and show he is exactly who we have always known him to be,” Ms. O’Malley Dillon said. She later drew a comparison to Barack Obama’s struggles in his first debate in 2012, though she conceded that the campaign had “more work to do because the president is 81.”

The most revealing aspect of the call was the decision to host it at all — a recognition that the Biden team knows it is being scrutinized by its own supporters. In the days after the debate, the communication from the Biden brass has been inconsistent, but improving, Biden fund-raisers say. Some individual donors have received direct communication from campaign officials, and Biden fund-raisers say communication picked up over the weekend, according to people close to the conversations.

Ms. O’Malley Dillon was among the senior Biden operatives who, the morning after the debate in Atlanta, offered some members of the National Finance Committee an “official NFC Debate Debrief” in the basement of the Ritz-Carlton, according to materials distributed to donors in advance. But many members of the committee skipped that summer N.F.C. meeting, meaning, as of Monday, only a select few had received formal instructions about how to talk about the president’s debate performance.

Still, Biden campaign fund-raisers leaped at the chance for engagement. The call, which was open to some people who did not technically sit on the N.F.C., was attended by hundreds of donors, some of whom had called in from vacation destinations around the globe.

Mr. Biden huddled out of sight at Camp David on Monday morning as his team remained defiant, promising that he would stay in the race despite last week’s debate showing. He plans to return to the White House on Monday evening, and he is expected to deliver remarks there on the Supreme Court’s ruling that former President Donald J. Trump has some immunity from prosecution on charges of trying to overturn the 2020 election.

Family members and friends spent the weekend urging Mr. Biden to keep fighting, even as some Democrats and others called on him to step aside. At the White House and the campaign, aides tried to press forward, putting out news releases on student loans and the president’s overtime policies.

But the week promised to be anything but business as usual.

Mr. Biden and his campaign aides are bracing for poll results this week that could show whether the shaky and disjointed performance in the debate has tanked his support with less than five months to go before Election Day.

Mr. Biden and his advisers discussed over the weekend whether the president should find a forum to respond to the debate fallout in person, by holding a news conference or sitting for interviews. But both options have political risks, and no decision had been made by Monday morning.

“Did you see Trump last night?” the president is shown saying during remarks he gave in North Carolina on Friday. “I mean this sincerely — the most lies told in a single debate. He lied about the great economy he created. He lied about the pandemic he botched.”

The ad ends with the president saying, “I know, like millions of Americans know, when you get knocked down, you get back up.”

Mr. Biden delivered a more forceful and disciplined speech at the North Carolina rally. Some of his political allies have said that they hope to see more of such demonstrations to show that Mr. Biden still has the vigor to serve as president for the next five years.

“He needs to be extraordinarily aggressive — much more aggressive than he has been by getting out in front of the public,” Matt Bennett, the executive vice president of Third Way, a Democratic think tank, said on CNN. “Doing town hall meetings with voters. Doing sit-downs with reporters. Doing television interviews. Doing press conferences. He needs to prove that was one bad night and not a pattern.”

Ms. O’Malley Dillon also told donors that Mr. Biden has “put out robust medical records” citing a physical recently that was accompanied by a “seven-page memo.” The White House has not made Mr. Biden’s physician available to answer questions, unlike most previous administrations.

She said that Mr. Biden “is probably in better health than most of us. But he’s also 81, and he knows he has to prove that he can do this job from a stamina standpoint.”

On Tuesday, he is scheduled to receive a briefing on extreme weather conditions and participate in a private campaign fund-raiser. On Wednesday, he will host a Medal of Honor ceremony. And on Thursday, he will celebrate the Fourth of July with members of the military.

He has no events scheduled at the White House on Friday, when he is scheduled to return to his home in Wilmington, Del.

“We’re looking forward to it,” Ms. O’Malley Dillon said of the second debate.