Protesters targeted Mayor Zohran Mamdani at an Oct. 7 anniversary vigil in Union Square, accusing him of betraying the Palestinian cause. Some advocates said these protesters represent a fringe view. Omar Baddar noted the group "account for a small minority of the pro-Palestine movement in this country." Tensions remain high.

Palestinian advocates acknowledged the range of viewpoints within their movement but were dismayed by the vitriol directed at Mayor Zohran Mamdani, a longtime ally of their cause.

Some of the protesters who disrupted an Oct. 7 anniversary vigil in Union Square chanted in support of Hamas. Some called for the deaths of Israeli soldiers. And one group held a sign that depicted Mayor Zohran Mamdani rolling out a red carpet for Prime Minister Benjamin Netanyahu of Israel, a man the mayor has explicitly called "unwelcome" in New York.

The mayor, who has sharply criticized Israel and Mr. Netanyahu throughout his political career but has called the Hamas-led attacks in 2023 "horrific war crimes," stood stone-faced while an angry crowd of people who nominally shared his views on the war in Gaza accused him of betraying the Palestinian cause and supporting genocide.

The vitriol directed at Mr. Mamdani, one of the most high-profile pro-Palestinian elected officials in the United States, laid bare the divisions within a decentralized movement that helped propel the young Muslim mayor to City Hall and is now reckoning with its own growing influence as disapproval of Israel's conduct in Gaza becomes more mainstream.

The protesters cited a range of complaints, including Mr. Mamdani's meetings with President Trump, which the mayor has said are in the best interest of the city, and his recently announced plan to combat antisemitism, which includes funding for a Jewish community group that organizes the Israel Day parade.

"He's meeting with the very people who are perpetuating Islamophobia, and to be a Muslim and proudly stand by their side and shake their hand is disgusting," said Aidan Parisi, 29, who is Muslim and said he had voted for Mr. Mamdani but now opposed him.

On Thursday, some Palestinian advocates in New York and elsewhere said the protesters who denounced Mr. Mamdani represented a fringe view within their movement. They expressed dismay at the sight of him being pelted with invective at a vigil organized by a progressive group, Israelis for Peace, that was held to honor those killed both in Israel and in Gaza.

Omar Baddar, a Palestinian American activist on the National Policy Council of the Arab American Institute, said the protesters on Wednesday "account for a small minority of the pro-Palestine movement in this country."

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"I don't think that Mamdani is above criticism," he said. "But to call him a traitor and to charge him with responsibility for genocide seems completely unwarranted and totally over the top."

The demonstration at Union Square on Wednesday grew out of a rally outside City Hall earlier in the day that criticized both Israel and Mr. Mamdani, which was organized by several left-wing groups that have powered pro-Palestinian street protests in New York in recent years, including Within Our Lifetime and the PAL-AWDA.

The protesters who rallied at City Hall and marched to Union Square included members of several college chapters of the Young Democratic Socialists of America. The Y.D.S.A. had originally endorsed the demonstration but withdrew its endorsement after pressure from the New York City chapter of the D.S.A., which is a separate entity, according to a person familiar with the communications between the groups.

On Thursday, Grace Mausser, the co-chair of the city chapter, which counts Mr. Mamdani as a member, issued a statement distancing the group from the protest.

"N.Y.C.-D.S.A. was not an organizer or supporter of this rally," she said. "Our Palestinian liberation priority is stopping the genocide and the flow of weapons and money between the United States and Israel."

Mr. Mamdani's mayoral victory was fueled in part by the enthusiasm he created among progressives, including the growing number of Americans who object to Israel's military actions in Gaza. According to the Pew Research Center, polls show that a majority of Americans now hold a negative view of Israel, including majorities of adults under the age of 50 in both political parties. Among Democrats and Democratic-leaning independents, that number rises to 80 percent.

But the Israeli-Palestinian conflict has caused tension for the mayor again and again in the first year of his term as he tries to square his deeply held views with his responsibilities to a city that includes roughly one million Jewish people.

On Wednesday, the third anniversary of the Hamas-led terrorist attacks in Israel, those tensions boiled over again.

The mayor drew the ire of Jewish leaders early in the day with a statement that called the anniversary "profoundly painful" but mainly focused on Palestinian suffering in Gaza. By evening, the mayor was staring into the middle distance as hundreds of pro-Palestinian marchers screamed at him across a police barricade, calling him a traitor and a coward.

Mr. Mamdani addressed that anger at an unrelated news conference on Thursday, where he defended his handling of the anniversary and said Oct. 7 was "a day of profound grief for so many New Yorkers," including Jews and Palestinians.

"I believe there must be room to mourn every single life," he said. "There must be room to reckon with the way so many New Yorkers' lives have been shattered."

Raed Jarrar, the advocacy director at DAWN, a human rights group based in Washington, said there was a broad range of views within the pro-Palestinian movement, though he was quick to denounce chants supporting Hamas.

Nevertheless, he said it was "delusional" to think that Wednesday's events indicated that the movement had turned its back on Mr. Mamdani.

"Make no mistake: There are no actual divisions in the pro-Palestinian movement and the pro-peace-and-justice movement," said Mr. Jarrar, whose organization has lobbied the Mamdani administration on issues related to Israel, Saudi Arabia and Sudan. "No one really looks at Mamdani and sees him as an adversary or an enemy."

Several prominent Palestinian New Yorkers and activists expressed support for the mayor, including Mahmoud Khalil, a Columbia University graduate and pro-Palestinian campus activist who became the face of President Trump's immigration crackdown after federal agents arrested him at his apartment building.

Mr. Khalil, a legal permanent resident who had not been accused of a crime, was detained for 104 days. He has since filed lawsuits against the university, Trump administration officials, pro-Israel groups and a conservative think tank.

"Mayor Mamdani fought for my release when the Trump administration targeted me for defending Palestinian rights, and he has stood by me since," Mr. Khalil said in a statement on Thursday. "I believe he is committed to accountability for Israel's ongoing war crimes and to advancing Palestinian rights, and I look forward to his office turning that commitment into more concrete action."

The Rev. Khader El-Yateem, a community activist in Brooklyn and the pastor of Salam Arabic Lutheran Church in Bay Ridge, said he thought Mr. Mamdani "did the right thing" by attending the Wednesday vigil.

Still, he hesitated to criticize the protesters who castigated the mayor. "All of us carry deep pain over what is happening in Palestine," he said, "but we don't necessarily agree how to respond politically."

Nevertheless, it pained him to see Mr. Mamdani accused of things he said were simply not true.

"I don't believe Mamdani is a Zionist," Pastor El-Yateem said. "I would love to see more elected officials speak about Palestinian suffering and genocide and ethnic cleansing. That is what we need to focus on."

Mr. Jarrar, a Palestinian American who immigrated to the United States from the West Bank city of Jenin, said many people were anguished over Israel's continuing military action in Gaza and the wars in Lebanon and Iran. He said he suspected that many of the protesters on Wednesday were young and frustrated with their elected officials, even those with whom they broadly agreed.

"It is interesting as a 48-year-old man to have a conversation about this with a 20-year-old Palestinian," he said. "A few decades ago, I viewed myself as a firecracker, a real hothead activist. But there are different experiences among those of us within the pro-Palestinian movement."

Wesley Parnell and Benjamin Oreskes contributed reporting.