The former vice president appeared relaxed and energized, greeting by first name many who had gathered at the Philadelphia home of a Comcast executive just hours after the launch of his 2020 presidential campaign.

The guests included well-known party fundraisers, a health insurance executive and Democratic lawmakers. The price of entry was $2,800, the maximum donation to a primary campaign. The event raised about $700,000, according to an organizer, boosting Joe Biden’s first-day haul to the front of the pack at $6.3 million.

Biden entered the presidential race last week with a unique fundraising advantage over his 19 competitors for the Democratic nomination: a sprawling network of the party’s most aggressive fundraisers who raised six to seven figures for Barack Obama and were readying to collect checks for Biden as he prepared to announce his third bid for the presidency.

But his approach also serves as a test of whether Democratic voters, wary of the political influence of wealthy corporate interests, will be turned off by a candidate so openly courting big donors. Most of the other Democratic hopefuls have focused on attracting large numbers of smaller contributions from online donors.

“I think what Joe Biden has to recognize is that it’s not 2008 anymore, and people are paying attention to where the money that funds you comes from,” said Charles Chamberlain, chairman of the liberal political action committee Democracy for America.

Many of Biden’s most ardent backers believe he can attract both the big donors whose support has traditionally given candidates a leg up and the smaller donors whose support has become a litmus test for presidential hopefuls.

“I think Joe Biden will do extremely well when it comes to fundraising, both at the grass-roots level and through traditional fundraising events, and that’s because Joe’s well of support runs extremely deep,” said Jon Cooper, a major Obama bundler in New York who led the effort in 2016 to draft Biden to run for president.

Biden’s advantage with large donors will help him as he seeks to outlast a crowded Democratic field. The eventual nominee will be up against President Trump, a formidable fundraiser.

Biden’s connections to wealthy donors could also place pressure on other Democrats to step up their big-money fundraising. The staff of former congressman Beto O’Rourke (Tex.), for example, previously noted they have not yet held private fundraisers. But O’Rourke is scheduled to meet privately with donors on May 13 in New York City.

Biden is not alone in courting maxed-out donations at private fundraisers. Most other campaigns are building a network of wealthy donors on their own.

Nonetheless, his fundraiser drew attention from other campaigns, including from Sen. Bernie Sanders (I-Vt.), who sent a fundraising email referring to the “fundraiser hosted at the home of a telecommunications lobbyist.”

Alan Kessler, a Philadelphia lawyer and Obama bundler who co-hosted the April 25 fundraiser, said it was unrealistic to expect candidates to reject bundlers.

“He has that cadre of people who are very loyal to him. Do you not call upon those people simply because they raise big money or bundle dollars?” Kessler said. “It’s unrealistic to expect that any of them would say no to that help if it was offered to them.”

Kessler, a friend of the Biden family, said about 175 people attended the event, and “in terms of Philadelphia and Pennsylvania, it seemed like every major Obama, Clinton fundraiser, without exception, was there.”

Many Obama bundlers feel a deep sense of loyalty to the vice president and believe he is the best suited to unseat Trump in 2020. They had declined to support any candidates or had donated to one or two candidates while waiting for Biden to make a decision.

“The fight’s on, and we’re helping everywhere we can,” said Steve Westly, former state controller in California and a major Obama bundler. “I think a lot of forces will come together to propel the vice president through the primary.”

But some are still hedging their bets, donating to other candidates even as they line up behind Biden. For example, some California-based Obama fundraisers are supporting both Biden and Sen. Kamala D. Harris (Calif.).

Others who had previously supported Obama have a different favorite: Pete Buttigieg, the mayor of South Bend, Ind., and a newcomer to national politics.

Some longtime Obama bundlers are helping Buttigieg at the urging of former Obama campaign operatives.

They contend that non-establishment Democrats are more successful — John F. Kennedy, Bill Clinton, Obama — than those considered to be insiders, such as Al Gore, John F. Kerry and Clinton.

One bundler, requesting anonymity to speak frankly about Biden, said Buttigieg reminds him of the energy that inspired him to raise money for Obama.

“I really like Joe Biden, but I’m really afraid his time may have passed,” he said.

Biden’s ability to raise and sustain large amounts of money for his own presidential campaign, particularly from small-dollar donors online, remains untested.

Biden’s 1988 and 2008 presidential campaigns relied on big donors and public funding. For his 2008 campaign, Biden raised $11.1 million, nearly a quarter of it transferred from previous campaigns or in public funding, according to data from the Campaign Finance Institute.

By the time he dropped out of the 2008 race, about 20 percent of his funds were from donations under $200 — a smaller share than Obama, former senator John Edwards (D-N.C.), Clinton and then-New Mexico Gov. Bill Richardson (D), data shows.

As Biden entered the 2020 race last week, he spent heavily on Facebook ads — more than $400,000 — ranking as the biggest 2020 spender on Facebook ads that week, data shows. Many of his Facebook ads were designed to raise money on the first day as a show of grass-roots enthusiasm out of the gate.

“We’re grateful and heartened by the influx of support from around the country,” particularly the online donors, said TJ Ducklo, Biden campaign spokesman. “We are confident that as more Americans hear Vice President Biden’s message, that energy and support will only continue to grow.”

In the meantime, party fundraisers fully on board with Biden are gearing up to collect big sums.

This month, Biden is scheduled to appear at a Los Angeles fundraiser at the Mayan-themed home of Obama bundlers James Costos and Michael Smith, according to an invite obtained by The Washington Post.

More than two dozen people are slated to co-host the event, many of whom were Obama 2012 bundlers. The minimum amount attendees must raise to become a co-host for Biden’s fundraiser: $10,000.