A coalition of progressive groups is demanding that Democratic leadership reject endorsements and outside spending by the American Israel Public Affairs Committee, the pro-Israel lobbying group that helped take down two members of the “Squad” in their recent primaries.

The letter, addressed to Democratic National Committee chair Jaime Harrison, exclusively shared with HuffPost, emphasizes that AIPAC’s reliance on large donations from right-wing donors and outsized attacks on the left wing of the Democratic Party.

“AIPAC and their allies are spending millions of dollars to defeat champions of the popular progressive agenda that voters demand and that help Democrats win, like Medicare for All, a Green New Deal, reproductive justice, transformative immigration and democracy reform, a lasting ceasefire, hostage deal, and halt on all weapons funding to the Israeli military’s assault on Palestinians in Gaza,” the letter says. “It will be significantly more difficult for Democrats to defeat Trump in November as long as the Party continues to allow GOP-backed PACs and corporate lobbies to have sway over Democratic politics.”

The letter comes after AIPAC and its affiliated super PAC poured more than $25 million into defeating two congressional progressives: Reps. Jamaal Bowman (D-N.Y.) and Cori Bush (D-Mo.). Bush and Bowman, members of the informal left-leaning group that named itself the Squad, suffered decisive losses as allies complained Democratic leadership had done too little to protect its incumbents.

The timing also falls just days before the 2024 Democratic National Convention begins in Chicago, where the party is hoping to project a unified front as Vice President Kamala Harris publicly accept the nomination for president. Few issues have riven the party like U.S. support for Israel and its deadly war in Gaza, which has killed more than 40,000 civilians, according to figures released Thursday by Gaza’s Health Ministry.

More than two dozen progressive groups co-signed the letter, including Justice Democrats, the Movement for Black Lives, the IfNotNow Movement, Sunrise Movement and the Working Families Party. Their coalition, Reject AIPAC, was organized as a counterweight to AIPAC but has not been able to marshal the same jaw-dropping levels of spending.

The ability of AIPAC, a single-issue lobbying group, to recruit candidates and deploy millions of dollars in primary contests where a wide range of progressive causes may be at stake has long angered the left wing of the party. Although AIPAC and its super PAC solicit donations from Republicans and Democrats alike, GOP mega-donors have furnished some of its largest contributions. When AIPAC has taken a stance in contested primaries, the group has almost always targeted progressive members of Congress who are not only critics of Israel but who have also led calls for wealth taxes, Medicare for All, and student debt cancellation ― all policies despised on the right.

AIPAC and its super PAC, United Democracy Project, have always maintained they support or oppose candidates based solely on their stance on Israel.

But after the Oct. 7 terrorist attacks on Israel, when AIPAC signaled its intentions to spend a record amount of money unseating critics of U.S. military support for Israel’s retaliatory offensive in Gaza, members of the left-leaning Squad and their allies began to air their frustration in public.

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

Still, few were willing to call on party leadership or other members to reject AIPAC outright. At the start of the primaries, just one Democrat in Congress, Bush, was calling explicitly for her fellow members to reject any support from AIPAC. A handful of her fellow progressives in the House, plus Sen. Bernie Sanders (I-Vt.), have since signed on to Reject AIPAC’s pledge not to accept AIPAC’s endorsements or contributions.

Although the party cannot stop AIPAC from spending unlimited funds in its primaries, it can discourage AIPAC-recruited candidates from entering primary contests, help incumbents fundraise, spend money in their defense and thwart AIPAC’s legislative goals if it continues to target party members.

In its letter, Reject AIPAC argues that resisting AIPAC’s interference in primaries is crucial to the long-term health of the party.

“They have sought to unseat the very candidates who energize the critical base that Democrats need to reach to win in November ― young people, progressives, and people of color,” the letter says. “The Democratic Party cannot rely on voters turning out in November on the top issues of reproductive rights, democracy, and peace while accepting donations and endorsements from a right-wing organization that is actively undermining those very principles.