Leading 2020 Democratic presidential candidates said Thursday that they wouldn’t be involved in a major pro-Israel conference over the weekend — a victory for progressive activists and a fresh sign of the party’s frustration with the U.S. ally’s hard-right drift.

Sen. Bernie Sanders (I-Vt.) “has no plans to attend the [American Israel Public Affairs Committee] conference,” Josh Orton, his policy director, told HuffPost in an email.

“He’s concerned about the platform AIPAC is providing for leaders who have expressed bigotry and oppose a two-state solution,” Orton continued, using an acronym for the group, which helps guide millions of dollars in political donations from supporters of Israel and has made its annual gathering a marquee Washington event.

Journalist Peter Beinart had earlier revealed that Sen. Elizabeth Warren (D-Mass.) would not attend. An aide to Sen. Kamala Harris (D-Calif.) told Politico she would play no role in the conference, either.

Former Housing Secretary Julián Castro also does not plan to attend, his deputy press secretary Sawyer Hackett said via email.

And Beto O’Rourke, the former congressman, will not be there, his senior adviser Rob Friedlander wrote in an email. Neither aide responded to a follow-up query about the reason for their respective candidates’ decisions.

Sen. Cory Booker (D-N.J.) will meet separately with constituents coming to Washington for the conference but does not plan to be involved with it in any other way, a campaign official told HuffPost on Friday. An aide to Sen. Amy Klobuchar (D-Minn.) said via email that she will do the same, and Jewish Insider reported that Sen. Kirsten Gillibrand (D-N.Y.) will too. Representatives for Rep. Tulsi Gabbard (D-Hawaii) did not respond to HuffPost’s requests for comment.

Pete Buttigieg, the increasingly prominent mayor of South Bend, Indiana, said last week that he would not attend the conference.

Former Starbucks CEO Howard Schulz, who is exploring an independent bid for the Oval Office, won’t go either ― though he did on Twitter slam other candidates who said they wouldn’t be involved.

On Wednesday, the advocacy group MoveOn revealed that 74 percent of its millions of members want progressives seeking the Democratic presidential nomination to skip the AIPAC confab.

MoveOn listed four reasons why candidates should do that: the group’s activism against President Barack Obama’s nuclear agreement with Iran; its past tolerance of anti-Muslim and anti-Arab rhetoric from its allies; its invitation to Israeli Prime Minister Benjamin Netanyahu, on whose watch U.N. investigators say Israeli soldiers may have committed war crimes; and its failure to criticize top Republicans accused of anti-Semitism, like Steve Bannon.

Many Democrats are also angry with pro-Israel figures for pressuring Rep. Ilhan Omar (D-Minn.) over her comments that money in politics compels U.S. fealty to Israel and makes debate over its policies difficult, organizers and Capitol Hill sources say.

Democratic aides and activists note that Omar did not specifically accuse Jewish people of creating that situation and that more direct GOP references to hateful historic tropes have often been ignored. Like Sanders, they say the underlying question of how the U.S. can promote a two-state solution for Israelis and Palestinians after unprecedented pro-Israel moves by President Donald Trump remains overlooked.

Instead, discussion of Omar and the prospect of a different U.S. policy approach to Israel remains mired in charges of anti-Semitism, though Omar herself has explicitly stated that she supports Israel’s right to exist. Adam Milstein, a donor closely tied to AIPAC, accused Omar and her fellow Muslim American lawmaker Rep. Rashida Tlaib (D-Mich.) this week of being “anti-Semitic and anti-Israel” and members of the Muslim Brotherhood movement, boosting a standard smear that casts Muslims as not truly American. He has since withdrawn from this weekend’s conference.

Netanyahu will visit the White House while in town for the gathering. The Israeli leader froze out Obama in his final term but has developed close ties to Trump and other world leaders linked to nationalist ideologies, despite how such thinking often demonizes Jews. Top Trump appointees, from Vice President Mike Pence to multiple aides in the administration, will be speaking at the AIPAC meeting, as will House Speaker Nancy Pelosi (D-Calif.), Senate Minority Leader Chuck Schumer (D-N.Y.) and powerful Democrats in both chambers.

While the Thursday announcements were striking, the bigger test will come at next year’s session of the AIPAC conference, when Election Day is closer and keeping influential Israel advocates, as well as more leftist voters, onboard will seem more critical to Democratic candidates. Sanders made waves when in 2016 he skipped the event to continue campaigning. However, he did have his speech passed out among attendees and had offered to address AIPAC via video.

Trump and the GOP also seem set to make support for Israel a major campaign issue, building on their assault on Omar by asserting Democrats are becoming dangerously anti-Semitic. The president is continuing to upend longstanding U.S. policy to show he’s more supportive of Israel than his predecessors. On Thursday, as his 2020 challengers grappled with the question of the conference, he announced that he would recognize Israel’s occupation of Syria’s Golan Heights as legal ― unlike any other major U.S. ally or world power.

This is a developing story. Please check back for updates.