New York City Mayor Zohran Mamdani is seeking to put his stamp on the city’s congressional delegation with a trio of endorsements against incumbent lawmakers and their picks, a move that could further expand the power of his democratic socialist movement or thwart its progress — and dent his own image in the process. Subscribe to read this story ad-free Get unlimited access to ad-free articles and exclusive content. “This is high-risk, high reward,” said Rebecca Katz, a prominent Democratic strategist and ally whose firm worked with Mamdani during his 2025 run. “He’s not afraid to take some big swings.” Politically, the endorsements are Mamdani’s biggest swings yet as mayor. He is backing former New York City Comptroller Brad Lander, who joined forces with Mamdani in last year’s mayoral election, in a contest to oust Rep. Dan Goldman in a district split between Manhattan and Brooklyn. In another Brooklyn and Queens seat, Mamdani is backing state Assembly member Claire Valdez in a contest against Brooklyn Borough President Antonio Reynoso — the choice of the district’s …