The outgoing congresswoman at first wanted a woman to succeed her — specifically, a woman of Puerto Rican descent, like her. According to multiple people familiar with what happened, Mamdani was clear that two people who fit that bill with deepest ties to the district, city councilwoman Tiffany Caban and state senator Julia Salazar, were not acceptable because despite their own DSA ties, they’d initially been skeptical of his mayoral run, worried he would lose and set the democratic socialist project back.

As he did, Mamdani warmed to Claire Valdez, a one-term assemblywoman without much of a legislative record but who’d been out early for him in the mayoral race. He knew by then that Velazquez would be backing Brooklyn Borough President Antonio Reynoso.

Mamdani kept asking Velázquez to hold off in going public for Reynoso, including the day before an interview he had conducted was published in which he was endorsing Valdez, which he didn’t tell her about.

Velázquez found out about the endorsement the next morning. She canceled a dinner they had scheduled for that night.

Three months later, Velázquez said she’s still too mad to talk about it.

“All I can tell you is the dinner didn’t happen,” she said.

Mamdani may have also done damage with some key Black and Latino leaders.

One particularly notable critic of his endorsements in Tuesday’s primaries was New York Attorney General Letitia James, a key backer during his campaign.

“Some of the candidates that he has supported are individuals who do not understand the politics of New York City, the cultural differences from district to district, who have not been part of the history and the struggle of some of these districts, and are relatively new to the body politic,” James told CNN, pointing particularly to what she said was Mamdani’s lack of understanding of race and class issues that run deep.

James said she and other political leaders she’s spoken to are “disappointed” in Mamdani.

“All of us are a little frustrated with the Democratic Party. But you don’t blow it up. That’s what MAGA has done,” James said.

Standing in Brooklyn on Tuesday with James and Reynoso, Jasmine Gripper, the state director of the Working Families Party — the powerhouse pushing New York politics to the left for 25 years until Mamdani’s win elevated the DSA — tried to be diplomatic, including when acknowledging the annoyance at DSA supporters who felt the WFP should have gotten behind Valdez and Avila Chevalier.

“DSA has a project to elect socialists. The Working Families Party has a project around building governing power on a broad coalition to deliver for working families. There are times where that project is parallel and aligned and united, and that’s great. And then there are times when we differ,” she said. “I hope we can learn to fight cleaner races. I think this one got a little bit too personal, too dirty. And so I hope that’s a lesson we all learn.”