Mamdani announced Bisgaard-Church’s appointment on Monday, alongside naming Dean Fuleihan, a former aide to former New York Mayor Bill de Blasio, as his first deputy mayor. Mamdani has been building his transition team and mayoral administration since beating former New York Gov. Andrew Cuomo, who ran as an independent, in the general election last week.

Mamdani praised the two appointments in a statement shared with the Washington Examiner.

“The work of government begins here, by ensuring that those we choose to lead it do so with a singular goal: delivering for working New Yorkers,” he said. “With Dean Fuleihan as First Deputy Mayor and Elle Bisgaard-Church as Chief of Staff, I have no doubt we will build a powerful and competent administration that delivers an affordable, livable city for working people.”

Bisgaard-Church said it was “the honor of a lifetime” to lead Mamdani’s campaign.

“Now, with sleeves rolled up, I look forward to delivering on the Mayor-elect’s affordability agenda and demonstrating what a well-run City Hall can do for everyday New Yorkers,” she said in a statement.

Bisgaard-Church’s appointment comes after the fellow young socialist’s campaign prowess guided Mamdani to City Hall. A source close to the Mamdani campaign called her the “real force behind bringing together all the different pieces from field to communication, and beyond.”

She began her career as Mamdani’s New York Assembly chief of staff in 2020 before being named his primary campaign manager. After his win, she shifted to a role as Mamdani’s senior adviser.

During it all, Bisgaard-Church kept a low profile. She doesn’t have an X profile, like many New York politicos do, and doesn’t mix in the social circles of the city’s political powers. However, she largely deserves the credit for Mamdani’s platform, allies said.

“Her influence cannot be overstated,” Gustavo Gordillo, co-chairman of the New York City Democratic Socialists of America, told the Observer. Bisgaard-Church is also a DSA member.

“She should take credit for the top three demands that make up the affordability agenda. With Zohran, she is the brains of the campaign,” Gordillo said.

Bisgaard-Church was behind the campaign’s social media presence, which helped launch Mamdani to prominence. She said the guiding words of the campaign were “consistency, clarity, authenticity.”

Those words aimed to distill complex policy in an entertaining way. Mamdani’s hallmark campaign promises — fast and free buses, a rent freeze for rent-stabilized tenants, and no-cost childcare — consistently resurfaced at the forefront of his campaign.

Mamdani insisted he would not have won without Bisgaard-Church.

“She has been at the heart of the things that I’m most proud to have accomplished,” Mamdani said. “I would not have won this race without her steering our campaign.”

Now Bisgaard-Church will turn to helping the mayor-elect govern. As Mamdani quoted former New York Gov. Mario Cuomo as saying, “While you campaign in poetry, you govern in prose.”

As of last month, she has been working to mold Mamdani’s transition, according to City & State. She has been meeting with current and former city, state, and federal officials as well as “interested individuals who are seeking to volunteer their time and insights, and excited individuals beyond that.”

Bisgaard-Church was also responsible for vetting possible deputy mayors, agency heads, timelines, and policies, according to the outlet. She hasn’t strayed from her DSA roots either, meeting with the organization weekly.

Gordillo also praised Bisgaard-Church for her work ethic, determination, and ability to mediate conflict.

“She is an extremely hard worker, constantly thinking about how we can win and how we can expand our coalition, and has always prioritised consensus among the different parts of Zohran’s constituency,” Gordillo told the Observer.

“She’s also very skilled at handling internal disagreements, which I think is a reason why we saw so much left unity around Zohran’s campaign,” he added.

It’s unclear who the Mamdani transition will go after next for top appointments, but many of those already chosen originated from de Blasio’s administration. Fuleihan, who was de Blasio’s top budget adviser, is an indication that the trend will continue.

He said in a statement that he was “grateful to help build and carry out this vision for a new era of leadership, and to ensure that City Hall deploys all of the tools at its disposal to deliver on Zohran Mamdani’s affordability agenda.”

Mamdani suggested he will aim for excellence in his appointments to City Hall.

“Excellence is not abstract — it will be reflected in the highest levels of City Hall and the advisers who will most shape my decision making,” he said during his announcement.

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And if one thing is certain, it’s that Bisgaard-Church’s influence will be felt with each person placed in the administration.

“No one does it better than Elle,” New York political forecaster Michael Lange wrote on X after her appointment. “The insiders already know. Soon, the masses will, too.”