Mamdani, a democratic socialist, added to his margin of victory over former Gov. Andrew Cuomo after the ranked-choice votes were redistributed.

Mr. Mamdani’s victory upended city politics and reverberated nationally. He relied on a memorable message, charisma and a strong ground game.

New York State Assembly member Zohran Mamdani was way ahead after ballots were counted last week, but the city’s ranked choice system meant he could not clinch the nomination until second-choice votes were counted Tuesday.