Adriano Espaillat

Justice Democrats, the organization that helped power Representative Alexandria Ocasio-Cortez’s rise to Congress in 2018, will test New York City’s political climate and throw its support behind an insurgent challenger to Representative Adriano Espaillat.

That candidate, Darializa Avila Chevalier, a Harlem-based organizer, will receive the group’s first endorsement in New York City for the 2026 midterms, and its fifth in a new crop of progressive challengers to establishment moderates in Congress.

The endorsements in New York are an effort to capitalize on the momentum generated by Mayor-elect Zohran Mamdani, a democratic socialist who pledged that the success of his campaign and administration would prove that the party’s left flank, once considered flailing and overly idealistic, could deliver on its ambitious policy goals.

Ms. Avila Chevalier, 31, said that both Mr. Espaillat’s record and Mr. Mamdani’s successful mayoral campaign had compelled her to run. Her 71-year-old opponent, she said in an interview, has been more beholden to corporate interests than to the needs of the district’s working-class families.

“He takes money from the very institutions that are making life harder for New Yorkers here — institutions like landlords, AIPAC and corporate PACs — and turns the other way when our rents are being raised, when we’re being priced out of our communities,” she said, referring to a prominent pro-Israel lobbying group. “And I think New Yorkers are hungry for something different. I think this past mayoral election proves that.”

Mr. Espaillat was not immediately available for comment.

Ms. Avila Chevalier’s run is one of a handful of primary challenges against well-known Democrats in the city that have emerged since Mr. Mamdani’s victory. The leftist city councilman Chi Ossé has said he plans to run against Representative Hakeem Jeffries, the top House Democrat, in his Brooklyn district; the city comptroller, Brad Lander, is preparing a run against Representative Daniel Goldman, a moderate Democrat representing parts of Brooklyn and Lower Manhattan.

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