Progressive lawmakers who have condemned Israel’s assault on Gaza are demanding Democratic leadership do more to combat a multimillion-dollar election-year backlash funded by the American Israel Public Affairs Committee, Washington’s most powerful pro-Israel group.

Several House incumbents, including some of the party’s rising progressive stars, are facing primary challengers funded by AIPAC, which has raised millions from Republicans. The three largest individual donors to its super PAC, United Democracy Project, are longtime Republican supporters who have given the party millions of dollars, its latest disclosures showed.

Rep. Cori Bush (D-Mo.), whose challenger is courting pro-Israel donors, called for Democratic primary candidates to reject AIPAC’s help outright.

“It’s simply not good enough for Democrats to run against Donald Trump and his MAGA extremist allies while running toward right-wing, dark-money groups like AIPAC,” Bush said.

Other incumbents are warning that by doing nothing, the party is allowing GOP mega-donors to try to dictate the winners of Democratic primaries.

“It’s a Trojan horse — it’s a way to smuggle Republican money into Democratic primaries,” Rep. Mark Pocan (D-Wis.), a vehement AIPAC critic, told HuffPost. “People should have to answer for taking that toxic money.”

AIPAC is the premier lobbying group protecting the United States’ political and military alliance with Israel. It has held bipartisan sway for decades. But Israel’s devastating offensive in the Gaza Strip has placed its deep ties to the Democratic Party under growing strain.

Plenty of special interests donate to one candidate over another. But no outside group has made it its mission to hand-pick primary winners with the same relentlessness as AIPAC and its affiliates. In 2022, United Democracy Project spent $26 million targeting just eight congressional candidates who publicly repudiated Israel’s treatment of Palestinians, helping to defeat six of them.

AIPAC has exclusively targeted progressive Democrats and has never inserted itself into a Republican primary.

This year, the group is fixated on unseating members of the so-called Squad, including Reps. Bush, Ilhan Omar (D-Minn.), Summer Lee (D-Pa.) and Jamaal Bowman (D-N.Y.), who are among the most outspoken critics of Israel’s strikes on Gaza. Donors associated with the group have reportedly offered to raise up to $20 million for candidates willing to challenge Rep. Rashida Tlaib (D-Mich.), the only Palestinian American member of Congress.

“They’re trying to make our elections auctions,” Pocan said.

In recent weeks, one lawmaker facing AIPAC attacks canceled their payment of quarterly dues that all Democratic members of Congress pay to the Democratic Congressional Campaign Committee, a campaign aide told HuffPost, in order to conserve cash for the onslaught.

“I don’t know how anyone running as a Democratic primary challenger could possibly want to be on the same side as Donald Trump and his January 6 insurrectionists,” said Lee in a statement as she faces another primary challenger after AIPAC spent $4 million trying to defeat her in 2022. “Their Republican billionaires want to use Israel as a political football to divide & distract us from being able to talk about the issues the majority of our constituents care about.”

Progressives have repeatedly pleaded with House Minority Leader Hakeem Jeffries (D-N.Y.) and other party leaders behind closed doors to stand up for incumbents who are coming under fire.

Jeffries endorsed Lee earlier this month. In 2022, a political action committee Jeffries started made modest donations to her and other candidates as a signal of his support.

But candidates facing the AIPAC onslaught want more.

Bush faces a primary challenge from St. Louis County prosecutor Wesley Bell, who abruptly dropped a months-long Senate campaign because he was motivated to run by a need “to stand with our allies, and Israel has always been an ally,” he told The Washington Post.

“We have had these conversations [with leadership], and personally I’ve just never gotten to a place where we’ve heard there’s going to be some change,” Bush told HuffPost. “We have heard them say, ‘We get it.’ … I haven’t heard any conversation that, as a caucus, we’re going to say, ‘No, we’re not going to continue to be an ally with AIPAC unless they do x.’”

Party leaders have taken shots at “outside groups” without naming AIPAC and, according to Pocan and other sources, have privately taken AIPAC to task for influencing its primaries.

But it is not clear if leadership will use every tool at its disposal, such as campaigning alongside embattled incumbents, pressuring major donors to support them and discouraging Democratic consultants from working with their challengers.

The party or its candidates could also condemn AIPAC’s spending outright, although the Democratic National Committee rejected a ban on dark money in the primaries last year.

“I would like to see the Democratic Party reject dark money in the primary,” said Matt Duss, the executive vice president of the progressive Center for International Policy and until recently a foreign policy adviser to Sen. Bernie Sanders (I-Vt). “We don’t have to disarm in the general, but we can decide to run clean primaries if we want.”

Progressive activists note that AIPAC’s Republican donors essentially book two advantages: defending the U.S.-Israel pact and eliminating some of the brightest stars on the insurgent left.

“What is more attractive to Republican mega-donors than defeating progressive Democrats in Democratic primaries?” said Usamah Andrabi, a spokesperson for Justice Democrats, a grassroots group supporting several besieged progressives. “These are the same billionaires who oppose wealth taxes, “Medicare for All” and student debt cancellation. … Of course they would love to defeat the small group of progressives in Congress who stand up against billionaires.”

The top GOP mega-donors backing AIPAC’s super PAC include Home Depot co-founder Bernie Marcus, who has given United Democracy Project $2 million. Marcus, whose estimated net worth is $6.3 billion, has plowed millions of dollars into super PACs supporting Trump and Republican efforts to control the House and Senate.

Michael Leffell, a wealthy investor, has donated $1 million to United Democracy Project and poured more than $1.2 million into Republican candidates and causes. Two notable exceptions include support for Bowman’s two previous Democratic primary challengers. Leffell lives in Westchester County, in the wealthy half of Bowman’s New York district.

Ed Levy Jr., UDP’s third-largest donor in the first half of 2023, has donated millions to Republican campaigns. Levy also served as AIPAC’s president in the 1980s and sparked an organization-wide clash when he sought for AIPAC to openly encourage members to vote for George Bush for president.

Levy, a construction magnate, has also donated to Democrats but under peculiar circumstances.

In 2022, he gave to Adam Hollier, a Michigan Democrat who received more than $4.1 million in support from AIPAC’s super PAC when he ran for Congress.

Hollier claimed that he “woke up one day” to a massive TV blitz in his favor and that its support blindsided him. But local reporters noted that as a state senator, Hollier sponsored a bill that would have rescued an embattled Levy Co. mining project by neutralizing a local environmental campaign.

Levy and another company executive donated $375,000 to AIPAC’s super PAC shortly after Hollier announced his run for Congress and made direct donations to Hollier’s campaign.

“Levy is a Republican donor, but … he doesn’t get to say where they’re going to spend it,” Hollier told Haaretz at the time. He lost the primary to self-funded dilettante Shri Thanedar.

In 2022, some of the largest AIPAC donors included WhatsApp co-founder Jan Koum, who gives mainly to Republicans, and Paul Singer, one of the GOP’s single largest donors.

Other top AIPAC donors include Larry Mizel, a Colorado homebuilder who has made lifetime contributions to the GOP of more than $5.5 million and was one of Trump’s earliest supporters, and Roger Hertog, who has given Republicans more than $3.5 million and has donated to Sen. Tim Scott (S.C.), former South Carolina Gov. Nikki Haley and Florida Gov. Ron DeSantis as they sought the party’s presidential nomination.

In a statement, AIPAC spokesperson Marshall Wittmann rejected the idea that it targets candidates for any other reason than their stance on Israel.

“Our sole criteria on supporting candidates from both parties is their position on the U.S.-Israel relationship,” he said. “In fact, we are one of the largest contributors to Democratic congressional candidates. It is entirely consistent with progressive values to stand with Israel, and we proudly and actively support pro-Israel progressives.”

He added that reports of AIPAC donors offering to raise $20 million for whoever volunteers to challenge Tlaib are “completely false.”

Openly plowing millions into contested elections is a new strategy for AIPAC. Before it founded the United Democracy Project super PAC for the 2022 midterm elections, AIPAC quietly directed huge sums of money by encouraging a large, diffuse network of pro-Israel groups and donors to give to its favored candidates.

The group has carefully guarded its bipartisan reputation and maintained strong ties to the Democratic Party. It donates handily to Jeffries and other leaders’ reelection campaigns and supports pro-Israel progressives.

Its money does not exclusively come from Republicans. AIPAC also courts major Democratic donors and has counterparts in the Democratic universe who oppose many of the same progressive candidates, such as Democratic Majority for Israel, a super PAC with close ties to AIPAC.

But in recent years, AIPAC has made more and more one-sided alliances with conservatives.

The group has repeatedly sided with Israeli Prime Minister Benjamin Netanyahu’s right-wing government in clashes with Democrats in the U.S., as when it mobilized congressional opposition to President Barack Obama’s nuclear deal with Iran. And in 2022, it endorsed 109 Republican members of Congress who supported overturning the results of the 2020 presidential election in order to keep Trump in the White House.

“I think [Democrats] are willing to accept it because it benefits them — until it doesn’t,” Andrabi, the Justice Democrats spokesperson, said.

Some believe the unfolding war in Gaza and AIPAC’s attacks on the war’s loudest critics will ultimately drive a wedge between Democrats.

Polls show unconditional support for Israel is collapsing among younger Democratic voters.

“They’re losing an argument within the Democratic Party,” Duss said. “When you’re reduced to laundering GOP money into Democratic primaries, maybe you’re just not appealing to Democrats.”

Former Rep. Andy Levin (D-Mich.), whom AIPAC spent heavily to defeat in 2022, said the stakes are higher than just protecting a handful of incumbents.

For a single-issue outside group to spend so much in primary races is unusual. If AIPAC proves able to pick winners and losers, nothing would stop other special interest groups from doing the same.

“AIPAC may be the innovator here, but Big Pharma isn’t stupid, the fossil fuel industry isn’t stupid,” Levin said. “They’ll all get the idea: ‘Hey, let’s go pick the nominees for both parties.’”

Duss, the former Sanders adviser, argued that standing by while AIPAC knocks off progressive champions risks disenchanting a huge number of young, progressive voters.

“AIPAC is serving as the tip of the spear for the effort to crush an insurgent progressive wing of the Democratic Party,” Duss said. “You’re really going to tell all these young voters who represent the future of the party that there’s no place for them?”

But Democrats have been saying AIPAC’s right turn will have consequences for years. “The partisanship that is perceived as creeping into AIPAC’s decision-making will hurt them in the long run,” Rep. Lawrence Smith (D-Fla.) once told The Associated Press. That was in 1988.

“I’ve been around the block too many times,” said James Zogby, the founder and president of the Arab American Institute and one of the longest serving advocates for Palestinian rights in Washington. “Will it change? Yeah, nothing is eternal. But the amount of damage that can be done before change comes can be enormous.”

With uncertain support from leadership, progressives under fire are steeling themselves for the onslaught of millions in AIPAC money.

“Organized people beats organized money every time,” Bowman said. “The key here is for people to know what’s going on.”

Bush, who says she doesn’t know what to expect from her party besides an endorsement, is counting on the same ground game that launched her into office in 2020.

“This is an outside group of people who are not from our districts who are influencing the elections in a district where people have already made their decision about who they want to be their member of Congress,” Bush said. “And we’ve never left the ground.”