Zohran Mamdani has buzz and some momentum in New York City’s mayoral race. But can a 33-year-old democratic socialist — or anyone else — beat former Gov. Andrew Cuomo in the Democratic primary? Mamdani picked up a key endorsement Thursday from U.

The decision by Ms. Ramos, a state senator from Queens, is at odds with her frequent criticism of Andrew M. Cuomo, including comments questioning his “mental acuity.”

The progressive congresswoman is supporting the young Queens assemblyman’s upstart campaign in a crowded Democratic primary field.