A recent attack ad against progressive Squad member Rep. Summer Lee (D-Pa.) depicts her as a radical threat to Democrats’ agenda. As the ad pans over photos of pro-abortion rights protests, the Jan. 6 Capitol riot and former President Donald Trump, a narrator warns, “Our rights are under attack, our democracy at risk, and in this moment, Representative Summer Lee is opposing President Biden.” The spot concludes with a plug for Bhavini Patel, a Pittsburgh-area council member challenging Lee as a moderate alternative.

Ads like these, against progressive members of Congress like Lee, are standard fare in a Democratic primary. Except the donor behind these ads is Pennsylvania billionaire Jeffrey Yass, who is this cycle’s single largest donor to the Republican party and on the shortlist for Treasury Secretary in a second Trump White House.

Yass has lavished more than $1.8 million on the super PAC behind the ads, Moderate PAC, making him the PAC’s single largest donor by far. At the same time he is paying for ads invoking the specter of Jan. 6, in other words, he is closely tied to the man who instigated it.

“For me, it’s really the audacity,” Lee said in an interview. “They don’t support Biden. … Jeff Yass is supportive of an insurrectionist. For any candidate to use dollars coming from him to paint me as an extremist is really rich.”

Yass made his fortune as an international stock trader, and, ProPublica reported, by assiduously structuring his wealth to avoid high taxes. His trading firm, Susquehanna International Group, is a major investor in TikTok’s parent company, ByteDance.

Susquehanna was also the largest institutional investor in the shell company that took Trump’s social media company public, causing Trump’s net worth to skyrocket at a perilous moment for his personal finances. Yass was reportedly on the guest list for Trump’s high-dollar Palm Beach fundraiser that took place last week.

His support for Patel fits a larger pattern of Republican dollars sneaking their way into this year’s Democratic primaries. Earlier this year, progressives accused the American Israel Public Affairs Committee super PAC, which is nominally bipartisan, of laundering Republican billionaires’ money into Democratic primaries under the guise of supporting a moderate political agenda.

Members of the Squad, the high-profile group of Black and brown progressives who have not only led calls for a cease-fire in the war on Gaza, but also pressed Democrats to expand the social safety net and raise taxes on the wealthy, are among the group’s prime targets.

AIPAC spent roughly $4 million opposing Lee in her first election in 2022. And while they are sitting out her primary this year, having assessed her as too strong a candidate, Lee said Moderate PAC’s tactics are about the same.

“This is my second cycle dealing with disinformation and contorting the facts,” she said. Answering charges that she is insufficiently supportive of Biden, her campaign notes she has hosted several Biden cabinet members and Vice President Kamala Harris in her district, and appeared at party-led rallies for abortion rights. “They’re using dog whistles ― this idea that a Black progressive woman is vaguely too extreme to represent you in Congress.”

Moderate PAC launched in 2022 under Ty Strong, a former Booz Allen Hamilton analyst, who said the group would raise $20 million to protect moderate Democrats from progressive primary challengers. Yass, who gave $1 million in July, wound up being the group’s only donor in the 2022 midterms.

When the group ran its first ads against Lee earlier this year, Lee turned Yass’ apparent support into a line of attack on Patel: “Her entire campaign is backed by Republicans, yet she says I’m not a good enough Democrat,” Lee said in a recent debate.

At the time, Moderate PAC had not yet disclosed its donors. Strong took the opportunity to rebrand Moderate PAC not as Yass’ PAC but as a coalition of disgruntled Pittsburgh Democrats bent on ousting Lee.

New campaign finance disclosures filed Wednesday, however, revealed that Yass donated $800,000 to Moderate PAC, or roughly four out of every five dollars the group raised to fight in Lee’s primary, in late February.

The disclosure shatters several of Strong’s previous claims about Yass. In late March ― three weeks after Yass wrote a check ― Strong told The Washington Post that Yass was not behind the ads, instead citing two Pittsburgh developers, Todd Reidbord and Gregg Perelman, and the local chapter International Union of Operating Engineers.

Last week, Strong admitted to Politico that Yass had made a sizable donation. But he claimed he approached Yass only after raising money among Lee’s constituents, and said people in Lee’s district would ultimately donate just as much as Yass.

“He knew nothing about Summer,” Strong said. “And so it’s not Jeff Yass, it’s me and Pittsburgh who realized that this far-left member shouldn’t be representing a D-plus-eight district.”

In fact, the PAC raised only $233,944 from sources other than Yass ― not even half of the $586,843 it has spent so far in Lee’s primary. Many of the Democratic donors he name-checked in previous weeks gave Moderate PAC $5,000 or less; Perelman, the developer, does not appear to have donated at all.

Strong did not respond to a request for comment.

Patel, whose campaign cannot coordinate with Moderate PAC, initially seized on the idea that Moderate PAC was funded by local Democrats.

At a March 21 campaign event, Patel said it was “misinformation” to claim Yass was supporting her campaign.

“[The Moderate PAC] was actually funded by labor unions, interestingly,” she said. “Operating engineers gave to it, several other labor unions gave to it, there are local residents in this district who have given to that PAC to run the ads that they’re running. Jeffrey Yass has not given money to that, I’ve not taken money from Jeffrey Yass.”

In an interview this week, after Moderate PAC disclosed its donors, Patel said she agrees with Moderate PAC’s message that Lee is not sufficiently supportive of Biden. But she said she, like Lee, wishes Yass weren’t her supporter.

“I’m a lifelong Democrat,” she said. “Framing the conversation on anything else deflects from my ability to talk about my opponent’s record.”

Asked why she believes Yass is in her corner, she said she didn’t have an answer, and echoed what she said in that early April debate with Lee: “I denounce Donald Trump. I denounce Jeffery Yass.”