For every election since 2004, the Monogram Shop in New York’s East Hampton has sold “political cups” featuring the names of the presidential candidates. The cups can be seen at fundraising events across the Hamptons, one of the wealthiest neighborhoods in the country, where high-dollar donors mingle in the summer homes of the rich, the famous and the powerful. The cups aren’t looking good for Joe Biden.

The shop keeps count of how many cups are sold for each candidate, a very selective poll of the political climate each election. The cup count has only been wrong once, in 2016, when Donald Trump won.

This year’s count doesn’t bode well for Biden, whose cup counts have been down compared with Trump’s, especially after the president’s disastrous debate performance last month.

“Biden’s numbers going from the 28th of June are so dismal,” said shop owner Valerie Smith, upon studying the recent cup count tallies.

This election cycle, the shop introduced a new political cup, one embossed with the words “Let Us Pray 2024” in red, white and blue.

The day before the Fourth of July, the shop sold 133 Trump cups and 112 Let Us Pray 2024 cups. Just 13 Biden cups were sold.

As unscientific as the Hamptons cup count may seem, it tracks with some of Biden’s top donors calling for him to step aside and let younger candidates take the lead.

While Biden – so far – seems determined to tough it out, some donors and fundraisers are expressing their anxieties privately and hoping he will step aside of his own accord.

“My own instinct is that this isn’t done yet,” said one source close to Democratic fundraising efforts who requested anonymity.

Many donors found the debate “alarming”, especially Biden’s inability to call Trump out for his many lies. Then, at a fundraiser in East Hampton on 29 June, two days after the debate, Biden read from a teleprompter. “It was very odd and off-putting,” an attendee said.

“This is not about Biden, we believe that he’s been a great president,” the source said. “This is an existential moment … I don’t know if we can take four more years of [Trump].”

A “donor revolt” may seem a bit awkward in the Democratic party, given its criticism of the ultra-wealthy. But wealthy donors are key components to a candidate’s campaign. Any sign that they’re peeling away from a candidate is never good.

“The big donors tend to be more consistent and regular donors,” said Michael Kang, a law professor at Northwestern. “These tend to be your real loyal supporters that are putting their money where their mouth is.”

The turn in donor support has clearly shaken Biden’s campaign. On Monday, the president told MSNBC: “I don’t care what the millionaires say.” Yet hours later, Biden held a call with his national finance committee – a group of his biggest donors who have donated at least $47,900 to his campaign.

Biden told them that his one job is to beat Trump. “I’m the best person to do that,” he reiterated, according to reports, before saying: “We’re done talking about the debate.”

But some of Biden’s top donors still very much want to talk about the debate. The list of supporters calling for Biden to step aside has been growing in the two weeks since the debate.

Netflix co-founder Reed Hastings told ABC News that “Biden is unfortunately in denial about his mental state”. Tech billionaire Marcus Pincus told the Financial Times that he doesn’t “see how President Biden will ever get around this age competency issue at this point”.

On Wednesday, actor George Clooney, who hosted a $28m fundraiser for Biden in June, called on Biden to step aside as the nominee in a New York Times op-ed.

“It’s devastating to say it, but the Joe Biden I was with three weeks ago at the fundraiser was not the Joe ‘big F-ing deal’ Biden of 2010. He wasn’t even the Joe Biden of 2020. He was the same man we all witnessed at the debate,” Clooney wrote.

Biden’s campaign said that it’s seen an uptick in small donations since the debate, but without big donors, Biden could fall behind Trump in fundraising. Less money for a campaign means less advertising and a weaker campaign against Republicans. Down-ballot candidates, like those running for congressional seats, also rely on enthusiasm for a presidential candidate to help fill their own coffers.

“I think a lot of other candidates up for election this year are really worried about what’s going to happen to them if the top of the ticket doesn’t do well and doesn’t raise money, and the party has less money to support them,” Kang said.

The donor revolt only picked up steam after Biden’s gaff marred a post-Nato summit press conference on Thursday with the New York Times reporting donors had warned Democrats that they were withholding $90m as long as Biden remained their candidate.

Biden’s campaign has emphasized that some major donors have stuck with the president amid the revolt, including LinkedIn co-founder Reid Hoffman and philanthropist Amy Goldman Fowler, and that grassroots fundraising has surged post-debate.

But polls are showing voters, not just donors, have mixed feelings about Biden after the debate.

An ABC News/Washington Post/Ipsos poll published on Thursday found that 67% of voters said that Biden should step aside as the nominee. And this is alongside a handful of Democratic lawmakers who are publicly calling on Biden to step aside.

Amid the uncertainty around what will happen to Biden’s campaign, Smith, of the Monogram Shop, said she’s been thinking of how many more Biden cups to put on order before November. She recalled previous elections, when there were leftover cups after a candidate dropped out of the race.

During the 2016 election, “I learned my lesson with the Jeb Bush cups,” Smith said.