"Zohran Mamdani brings clarity, discipline, and a deep commitment to tackling the stubborn issues facing New York City," Espaillat said in a statement.

Education issues are at the forefront of the race as the United Federation of Teachers has decided to put its support behind the Queens assemblyman.

The selections could be especially consequential for Mr. Mamdani, a 33-year-old state lawmaker who is still trying to assure segments of his own party that he is prepared to lead the nation’s largest...