NEW YORK CITY—Support from New York City Mayor Zohran Mamdani paid off for two candidates so far this primary season, as he and the Democratic Socialists of America sought to defeat progressive candidates in Democratic primary races for seats in Congress. 
On the job for fewer than six months, the mayor waded into three congressional primary races, backing democratic socialists and progressives against more established Democrats.
Mamdani-endorsed former New York City Comptroller Brad Lander defeated Rep. Dan Goldman, whose seat spans lower Manhattan and part of Brooklyn.
In the race to succeed retiring Rep. Nydia Velázquez, Mandami-endorsed Assemblymember Claire Valdez, a self-described democratic socialist, beat Brooklyn Borough President Antonio Reynoso, who was backed by Velázquez. …