They’re hoping the former vice president can emerge as the moderate alternative to Bernie Sanders that some Democrats are desperately craving. And over the last three days they’ve rallied behind Biden, high off his solid Tuesday debate performance and promising-looking polling in South Carolina.

“People are beginning to believe we can get a big win here, and slingshot into Super Tuesday,” said Dick Harpootlian, a South Carolina state lawmaker and Biden bundler who has also contributed money to the pro-Biden super PAC. “A squeaker’s not going to do much for him. But I think he’ll do better than that.”

The weeks following Biden's loss in Iowa and New Hampshire represented a low point for the campaign. And Biden, who is more reliant than his competitors of support from big donors, needs a steady stream of contributors writing big checks in addition to online fundraising in order to run a campaign.

Like several other leading candidates — including Elizabeth Warren, Amy Klobuchar and Pete Buttigieg — Biden began February having nearly drained his campaign account in preparation for the Iowa caucuses. Biden had $7.1 million in the bank at the start of the month, more than Warren, Klobuchar and Buttigieg but far less than Sanders, who entered February with $16.8 million, and Bloomberg, who has poured more than $500 million into his campaign.

The Pro-Biden super PAC Unite the Country, which spent $4.5 million in Iowa, spent only $1.3 million on TV ads in the weeks that followed in New Hampshire, Nevada and South Carolina, according to Advertising Analytics. And after Biden’s poor performance in the Iowa caucuses, some of the former vice president’s donors privately weighed helping one of his rivals — often Mike Bloomberg, whose campaign has courted donor support even though the billionaire former New York City mayor is self-funding his campaign.

Biden’s campaign was the last major campaign to reserve advertising in Super Tuesday states, and those reservations were only a “low six-figure” digital ad buy made by the campaign this Wednesday.

But two days after the Democratic debate, as the campaign pulled in money from newly energized supporters, the campaign expanded its Super Tuesday plans, buying an additional $2 million in television ads in states including California, Texas, Virginia and North Carolina. The super PAC, too, expanded its original Super Tuesday ad buy, with both groups now funding last-minute ads ahead of next week’s 14-state mega-primary.

“To be honest, after New Hampshire, it was tough,” said Steve Schale, a strategist for the pro-Biden super PAC. “After the first few states, we tried to reassure people that things were going to be alright.”

But Biden has looked better on the campaign trail since then, Schale said.

“It’s not just the polls in South Carolina — people saw both debates, think he’s had a very good two weeks,” Schale said.

As he seeks to regain frontrunner status, Biden won’t be able to catch up financially to Sanders, who has spent more than $15 million advertising in Super Tuesday states, according to Advertising Analytics. Meanwhile, Bloomberg has aired $69 million in California ads alone, along with hundreds of millions more elsewhere, and by the end of Super Tuesday, more than one-third of the delegates available in the Democratic primary will be decided.

As Biden’s campaign struggled through February, Bloomberg was wowing elite Democratic donors across the spectrum with a series of meetings and cocktail hours in which Bloomberg or staffers laid out his campaign strategy and answer questions. Other donors took tours of the Bloomberg campaign’s Times Square office, wowed by the expansive open layout and encouraged by the campaign’s willingness to listen to their new ideas.

But this week, after Bloomberg’s rough debate performance, Biden allies argued the field needs to narrow and Bloomberg should consider bowing out.

“Joe Biden is demonstrating he can build the type of diverse coalition needed to win the nomination and defeat Trump, but as long as Mayor Bloomberg continues to divide up the non-Sanders lane, there is a very real chance the biggest beneficiary of his ads will be Bernie Sanders,” Unite the Country strategists wrote in a memo to donors that was obtained by POLITICO.

Jon Henes, a Democratic fundraiser who chaired Kamala Harris’ finance committee before helping Biden’s campaign, penned a lengthy email to friends and other Democrats on Friday in support of Biden and some down-ballot candidates. Henes argued that “we need our moderate candidates to come together for the good of the country and party” and that South Carolina can prove Biden is a unifier, according to a copy of the email obtained by POLITICO via a recipient.

“The polls and momentum seem to be behind Joe Biden,” Henes wrote. A victory in South Carolina will show Biden has “real grit and fight” by not giving up after his early losses, he continued.

“This separates him from the other moderates,” Henes wrote. As for Bloomberg, “an argument can be made that he should drop out and support Joe and pour all of his resources behind him.”

The day after Super Tuesday, Los Angeles Mayor Eric Garcetti and California Sen. Dianne Feinstein, both Biden supporters, will be among the hosts of a Los Angeles fundraiser for Biden held by former Paramount Pictures CEO Sherry Lansing.

Though the results of the Iowa caucuses were surprising, Biden’s campaign had long warned that Iowa and New Hampshire would not be its best states, said producer and talent manager Eric Ortner, a Biden fundraiser.

"It’s always been about delivering a winning campaign. Not about what donors may hear in the daily deluge of cable news," Ortner said. "The plan presented by [Biden campaign manager] Greg Schultz was always that the cycle really starts in Nevada and South Carolina.”