Black city leaders are worried their influence is waning at a moment when the rising costs that Zohran Mamdani put at the center of his campaign are pushing Black New Yorkers out of the city.

Mr. Mamdani is Muslim, and his faith played a role in expanding the diverse coalition that propelled his campaign.

Not so long ago, Mr. Mamdani was a little-known state assemblyman. But his personality and platform captivated an unlikely coalition of New York City primary voters.