Political upstart Zohran Mamdani secured another key endorsement Wednesday, earning the support of the United Federation of Teachers, New York City’s most powerful teachers’ union, a day after the president of the United States threatened to overtake the five boroughs should the 33-year-old be elected mayor.

Trump also reignited his long-standing feud with Washington’s Democratic leadership, suggesting his administration is weighing a federal intervention in the capital.

Mamdani, a 33-year-old state assemblyman representing northwest Queens, last month shocked the political establishment by trouncing the longtime front-runner, former Gov. Andrew Cuomo, whose name recognition, experience and support of billionaires and corporations, made him the favorite.