PHILADELPHIA — When 300 top fundraisers for Vice President Kamala Harris filed into Philadelphia’s Academy of Fine Arts on Sunday evening for a 10-to-a-table dinner, they got to hear from Gov. Josh Shapiro of Pennsylvania and Jaime Harrison, the chair of the Democratic National Committee.

The message from Harris’ surrogates to her top donors: Yes, you’ve raised a lot of money for us. Now, please raise even more.

The donors, dining on grilled cod and beef medallions, had good reason to chortle. Finance leaders had told them earlier that they had raised a staggering $1 billion for Harris’ campaign since she replaced President Joe Biden as the Democratic nominee.

The next day, campaign officials told donors in a closed-door briefing that they had raised well over $100 million in September for the campaign’s major donor program, according to two people briefed on their remarks.

All of this success has had some unintended consequences.

For starters, so much money has been raised that donors are occasionally reluctant to give more, according to several fundraisers and finance professionals serving Harris. Why give $3,300 — the maximum legal donation — in mid-October to a candidate raising millions of dollars a day?

And could a big contribution so late in the campaign even be put to use?

“Yes, I understand we have done good work in the fundraising space,” Rufus Gifford, the campaign’s top fundraising official, said. “I will never say it’s enough. Because with the stakes as they are, with the amount of dark money on the side, we’re up against a behemoth.”

Harris fundraisers said that complacency was by no means a dominant sentiment and that the campaign was still hitting its daily fundraising targets.

But there are signs that the campaign is concerned about creating the impression that it does not need more money.

Harris’ team has refused to reveal its September fundraising totals, even to donors Monday at their “fall retreat” at the Ritz-Carlton in Philadelphia. Her aides have typically announced her fundraising sums in the first days of the ensuing month, but they have held off longer than normal to avoid looking overconfident and dissuading donors, especially small donors, from giving more, according to three people familiar with the matter.

“We still have money to raise between now and Election Day,” Gifford said. “We still have a gap to make up in our budget.”

Gifford was among the campaign officials who spoke to the donors who gathered in Philadelphia over the Yom Kippur holiday weekend. They received an overview of public (but, to some donors’ chagrin, not private) polls, learned about the campaign’s TikTok strategy and ate lunch with Gwen Walz, the wife of Gov. Tim Walz, the vice presidential nominee, according to a copy of the agenda seen by The New York Times.

The lobby of the Ritz, a former bank a block from City Hall that is framed by 16 Ionic columns and a open-sky dome, doubled as a reunion spot for Harris loyalists. Fundraisers draped in “fall retreat” lanyards, camouflage Harris-Walz hats and “Kamala is Brat” buttons cavorted at a bar well past midnight as DNC chair Harrison dispensed hugs to old friends.

By day, they huddled in coffee meetings with officials from allied super political action committees and with Jeffrey Katzenberg, the Hollywood megabundler who is a co-chair of the campaign.

Some Harris supporters have worried that the campaign is raising so much money so close to the election that some of it will go to waste.

Joe Goldman, president of the Democracy Fund, started a fundraising drive called “All by April” this year to encourage liberal philanthropists and contributors to make donations to allied groups by April for precisely this reason.

“Voters don’t start paying attention until late, and donors often don’t start paying attention until late,” he said. “When money flows late, groups on the ground don’t have time to plan, don’t have time to hire up staff. When they’re receiving money in the summer and the fall, they have a limited number of things they can do with it. It is less and less efficient.”

Still, experienced campaigns strive to raise large amounts of money and, guided by accounting and budget officials, spend as many dollars as possible, ideally ending the campaign with close to zero in the bank.

The Harris team prebooked $370 million worth of fall television and online advertisements based on anticipated revenue from donors. Continuing to raise money will not necessarily expand those purchases, but it allows the Harris campaign to avoid embarrassing ad cancellations if some anticipated donations do not materialize.

Before the arrival of digital advertising, campaign veterans say, it was hard to put late money to use because direct mail and television ads require a longer lead time. Nowadays, money can be used instantly on digital ads or paid text and phone programs that can increase voter contact. In 2020, the Biden campaign entered October with $177 million on hand and managed to spend $417 million over the final weeks.

“A planned dollar is always going to be more efficient than an unplanned dollar,” said Danielle Butterfield, who runs Priorities USA, a digitally focused pro-Harris super PAC. “But smart campaigns have really rigorous and accurate projections as far as to how much they expect to come in the final weeks — so much that the money you’re contributing is already factored in.”

The large sums that the campaign has raised so late have also allowed Harris to add new members to her staff for stints as short as three to four weeks.

Fundraising events that feature a personal appearance from a candidate tend to raise significant money, but Harris is no longer on the fundraising trail herself. Her last appearances were two events in California in late September that raised $55 million.

Former President Donald Trump, on the other hand, still has to appear at fundraising events. He hosted a finance event at Mar-a-Lago on Wednesday evening, where he was expected to dedicate hours of his time to a roundtable discussion, a VIP reception and then remarks to a broader group. Some donors are flying down together on private jets to Florida just for the event.

Trump and running mate JD Vance are also hosting a reception before their appearance at Madison Square Garden in New York this month to raise more from donors, according to a copy of the invitation.