New York state Assemblywoman Claire Valdez has won the Democratic primary for the seat of retiring U.S. Rep. Nydia Velázquez with backing from New York City’s mayor.

The democratic socialist candidate defeated Brooklyn Borough President Antonio Reynoso on Tuesday, helped by endorsements from Mayor Zohran Mamdani and U.S. Sen. Bernie Sanders of Vermont. Both backed Valdez in a test of the political clout of the progressive left against the Democratic establishment in a series of New York primary contests Tuesday.

The outcome leaves Valdez in a strong position for November in the heavily Democratic district that covers parts of Brooklyn and Queens. It also marked a stinging setback for Reynoso, who had the endorsement of Velázquez.