“In this time of crisis in our politics, it is not surprising that those who are dedicated to defeating Donald Trump are organizing in every way permitted by current law to bring an end to his disastrous presidency,” she added. “Nothing changes unless we defeat Donald Trump.”

“Donald Trump has decided that the general election has already begun,” Kate Bedingfield, Biden’s deputy campaign manager, wrote in an emailed statement. “He and his allies are already spending massive amount of money on paid television and digital advertising to intervene directly in Democratic primaries with the goal of preventing Joe Biden, the opponent that Trump fears most, from becoming the Democratic nominee.”

The Biden campaign said President Donald Trump’s false attacks on the former vice president made it necessary for it to welcome the help of a super PAC. Trump, the Republican National Committee and other GOP groups have spent more than $10 million attacking Biden, with much of that money aimed at the four early primary states of Iowa, New Hampshire, Nevada and South Carolina.

Many Democrats view super PACs, which can raise and spend unlimited sums and often rely on checks worth tens of thousands of dollars from wealthy donors for funding, as a malignant force that represents a big-money era of politics the party is nominally dedicated to ending. Democratic candidates for president in 2020 have largely avoided super PACs, but Biden’s shift could lead more candidates to tacitly back outside groups. (Super PACs are not legally allowed to coordinate directly with campaigns, but an unkind word from a candidate is often all that’s needed to deprive them of funding.)

Vice President Joe Biden’s campaign said Thursday it would welcome help from a super PAC, a total reversal from Biden’s stance at the beginning of the campaign and a decision reflecting his diminished financial position in the 2020 Democratic presidential primary.

“By making big-money corruption the center of how he funds his campaign, Biden severely jeopardizes his legacy as Common Man Joe that he spent decades cultivating,” Green said. “If Biden cares about defeating Trump, he should not open the door to billionaires and corporations flooding the primary and should make clear he does not want his supporters to use big money to attack other Democrats.”

Biden’s decision drew nearly immediate condemnation from his progressive rivals in the 2020 campaign. Adam Green, a top ally of Massachusetts Sen. Elizabeth Warren, said Biden was putting his reputation as a longtime ally of the middle class at risk.

The campaign of Vermont Sen. Bernie Sanders, who attacked Hillary Clinton over her support from super PACs during the 2016 presidential election, aimed a similar volley at Biden.

“The former Vice President has been unable to generate grassroots support, and now his campaign is endorsing an effort to buy the primary through a super PAC that can rake in unlimited cash from billionaires and corporations,” Sanders campaign manger Faiz Shakir said. “That’s not how we defeat Trump. It’s a recipe to maintain a corrupt political system which enriches wealthy donors and leaves the working class behind.”

Biden’s decision comes as he falls behind the other candidates in the money race, even though he still leads in much of the public polling. His campaign has just $9 million on hand, the fifth-highest total in the 2020 Democratic primary field. Sanders has $33.7 million in the bank, and Warren has $25.7 million. Even South Bend, Indiana, Mayor Pete Buttigieg and California Sen. Kamala Harris, who are both well behind Biden in public polling, have more campaign funds than he does. Biden has struggled to raise money online from small-dollar donors at the same pace as his competitors, and many of his donors have already given the federal maximum of $2,800.

End Citizens United, a Democratic campaign finance reform group, criticized Biden for his reversal and said his fundraising struggles were no excuse. In a statement, it noted less than a month had passed since Biden last said he wouldn’t welcome a super PAC. At that time, Trump’s attacks on the former vice president had already begun.

“The path forward for his campaign depends on Democratic primary voters trusting that they’d have more say in a Biden administration than big money donors. It is incredibly disappointing to see Vice President Biden completely reverse his position now that times are tough,” said Tiffany Muller, End Citizens United’s president. “This is exactly the time he needs support from real people the most. We urge him to reconsider this decision and disavow this super PAC.”

While Biden’s campaign will dismiss much of the criticism aimed at his decision as coming from partisans who dislike his candidacy for ideological reasons or are backing his opponents, he can’t say the same of End Citizens United. The group, which has pressured all of the campaigns to reject single-candidate super PACs, is neutral in the 2020 presidential primary and helped many moderate Democratic candidates win House seats during the 2018 midterms.

If a super PAC forms to back Biden ― and it would be shocking if one did not ― he would become the second candidate in the field to welcome an outside group accepting massive donations. Businessman Andrew Yang welcomed the support of a super PAC earlier this week. A super PAC has formed to support New Jersey Sen. Cory Booker, but he has said he doesn’t want the group’s help. Washington Gov. Jay Inslee embraced the support of a super PAC before he dropped out of the race in August.

It’s not clear if Biden will appear at fundraisers for a super PAC. If a group begins raising and spending money during 2019, it will have to reveal its donors in January, before the first Democratic primaries in Iowa and New Hampshire.

Biden has a long history as a campaign finance advocate, and has been fiercely critical of super PACs in the past. During an appearance on “PBS NewsHour” in 2018, Biden said he told Sanders not to create a super PAC during his 2016 run.

“I’m the guy that told him, you shouldn’t accept any money from a super PAC, because people can’t possibly trust you,” Biden said at the time. “How will a middle-class guy accept you if you accept money?”

This story has been updated with additional information.