Zohran Mamdani has won a decisive victory in the primary race to become the Democratic candidate for the next mayor of New York City, according to The Associated Press, after building a commanding lead in first-choice results that shook the national political establishment.

Mr. Mamdani roundly defeated Andrew M. Cuomo in the Democratic contest, widening his primary-night lead by a significant margin once ranked-choice tabulations were run.

NEW YORK — Zohran Mamdani has won New York City’s Democratic mayoral primary, a new vote count confirmed Tuesday, cementing his stunning upset of former Gov. Andrew Cuomo and sending him to the general election.