On Jan. 1, Mr. Sanders will stand by Mr. Mamdani’s side once again, two democratic socialists on the steps of City Hall for a public swearing-in ceremony before a crowd of supporters that Mr. Mamdani’s team predicts will swell to a staggering 40,000 people.

The senator, who will administer the oath of office, said in an interview on Monday that if he also delivers remarks at the inauguration he is likely to focus on the “retreat” of democracy in the United States. He said that “working people” correctly perceive “that government no longer works for them, but just for wealthy campaign contributors and a billionaire class that controls the economy.”

Mr. Sanders administered the oath of office for Mr. de Blasio’s second term, and many of Mr. de Blasio’s former aides are involved in Mr. Mamdani’s transition.

When Mr. Cuomo decided to continue running in the general election on an independent ballot line, Mr. Sanders and Ms. James rode to Mr. Mamdani’s aid. Mr. Sanders repeatedly rallied with Mr. Mamdani, describing him as the “future of the Democratic Party” and assailing other party leaders for failing to immediate coalesce behind him. The two men share the view that “it is imperative that we have a government in New York City and around the country that represents working people and not just the oligarchs,” Mr. Sanders said on Monday, “not just the wealthiest people in the country or in the City of New York — who, by the way, did everything they could to defeat him.”

Dana Rubinstein covers New York City politics and government for The Times.

https://archive.is/t9Z5F#selection-749.0-757.153

The inauguration will include a traditional swearing-in ceremony on the steps of City Hall at 1 p.m., as well as a first-of-its-kind public block party along Broadway’s “Canyon of Heroes,” Mamdani’s transition team said.

The block party will have large viewing areas where attendees can watch the ceremony live. Attendance at the party is free but limited, and guests must RSVP through the transition website. https://www.transition2025.com/inauguration
The ceremony will also be livestreamed.

In a statement, Mamdani said the inauguration would reflect the priorities of his incoming administration.

“This inauguration is a celebration of the movement we built, the mandate we won, and the city we are prepared to lead,” he said. “Working New Yorkers are at the heart of our agenda, and we invite them to join us as we welcome this new era of politics to City Hall.”

https://ny1.com/nyc/all-boroughs/politics/2025/12/22/mamdani-to-be-sworn-in-as-mayor-by-bernie-sanders--letitia-james