New York’s new mayor challenged his supporters and his opponents to make the city better, and to hold him to account.

Mr. Mamdani, the city’s first Muslim and South Asian mayor, celebrated the city’s diversity and pledged to govern ...

Zohran Mamdani, the democratic socialist who campaigned on a promise to tackle the affordability crisis in one of America’s most expensive cities, vowed to govern “expansively and audaciously” as he ...