Sen. Bernie Sanders (I., Vt.) and former vice president Joe Biden both falsely claimed during Sunday night's Democratic presidential debate that they are not receiving help from super PACs and outside groups.

"Why don't you get rid of the super PAC that you have right now, which is running ugly, negative ads about me?" Sanders asked Biden.

"You getting rid of the nine super PACs you have?" Biden asked.

"I don't have nine—I don't have any super PACs," Sanders said.

Biden said Sanders's implication that he is aided by outside money and funded by wealthy donors is a farce.

But both candidates are receiving help from super PACs and outside groups.

Biden was referring to nine progressive activist groups backing Sanders: Center for Popular Democracy Action, Democratic Socialists of America, Dream Defenders, Make the Road, Our Revolution, People's Action, Student Action, Progressive Democrats of America, and the Sunrise Movement.

These groups are not super PACs. They are 501(c)3 and 501(c)4 nonprofits. Like super PACs, they are not bound by contribution limits and can collect unlimited sums from donors. But unlike super PACs, those nonprofits can—and do—hide the sources of their funds, a practice known as "dark money."

Johnny Verhovek, a political reporter for ABC, pointed out to Biden communications director Kate Bedingfield that these groups are not super PACs.

"These people or groups are essentially dark money groups that don't release their donors," Bedingfield said. "So I think the point the Vice President was making is that these groups are out there, they are not held accountable in the same way in terms of donor disclosure. And they are supporting Senator Sanders."

One of those groups, Our Revolution, was founded by Sanders and former aides. It is now working to increase voter turnout for his campaign. Due to its work supporting his candidacy, the group was hit with an FEC complaint alleging it has violated campaign finance laws by accepting contributions that surpass the federal limit.

Sanders is also receiving help from super PACs. The Vote Nurses Values PAC, for example, has spent nearly $800,000 supporting his candidacy, according to the Center for Responsive Politics.

Biden is backed by Unite the Country, a super PAC founded by Democratic operatives Matt Tompkins and Mark Riddle, which has spent $10 million backing his candidacy. The pair also founded Future Majority, a dark money group that will spend $60 million primarily in the Midwest region for the 2020 elections.