As an unapologetic democratic socialist, Mayor Zohran Mamdani is not afraid to defy the traditional political calculations. And that includes whether or not to attend the Met Gala, perhaps the premier event on the city’s social calendar and one that has regularly drawn a series of past mayors.

But that will not include Mr. Mamdani. On Thursday, the mayor confirmed in an interview with Hell Gate that he and his wife, Rama Duwaji, were planning to skip the event, a starry fund-raiser for the Metropolitan Museum of Art’s Costume Institute traditionally held on the first Monday in May.

The mayor framed his absence as a way to keep his focus on “affordability and making the most expensive city in the United States affordable.”

Representatives for the mayor’s office did not immediately respond to requests for comment on Thursday afternoon.

Past leaders of the city have made a point of attending the benefit as a show of support for one of New York’s oldest cultural institutions. Michael R. Bloomberg, Bill de Blasio and Eric Adams have all walked the museum’s famous staircase alongside celebrities, models, athletes, fashion designers and, increasingly, tech billionaires.

This year’s event will inaugurate the museum’s spring fashion exhibition, “Costume Art,” which opens on May 10 and will explore fashion’s ties to the world of art by juxtaposing 200 contemporary and historical garments and accessories with sculptures and paintings drawn from the museum’s collection. The event and the exhibition are sponsored by the billionaire couple Jeff Bezos and Lauren Sánchez Bezos, who will also serve as the evening’s honorary chairs.