President Donald Trump threatened to cut off federal support for New York City if the next mayor doesn't "behave."
Mamdani emerged as the almost certain winner in the ranked-choice Democratic mayoral primary last week, marking a stunning upset for the candidate who was largely unknown when the contest first began.
The final results have yet to be certified, but by the end of election day, Mamdani led the first-choice vote count with roughly 44 percent support, ahead former New York governor Andrew Cuomo, in second place at about 36 percent. Cuomo conceded to Mamdani on election night.
The president has previously threatened to cut funding for Democratic-led cities and states that oppose federal policies, including so-called sanctuary jurisdictions.
According to a report by the New York City comptroller's office, the city receives more than $100 billion through various federal entities and programs.
During Sunday's interview, Trump described Mamdani as a "pure communist" who is "very bad for New York."
“I will be the mayor for every New Yorker, whether you voted for me, for Governor Cuomo, or felt too disillusioned by a long-broken political system to vote at all,” Mamdani said after the polls closed. “I will work to be a mayor you will be proud to call your own.”
Mamdani, 33, has served as a member of the New York state Legislature since 2021. The self-proclaimed Democratic socialist was born in Uganda and raised in New York City.
Some say Mamdani’s success in the Democratic primary race could be attributed to the baggage of his main opponent Cuomo.
After a high-profile sexual harassment accusations in 2021 Cuomo ultimately resigned as governor.
Sen. Bernie Sanders (I-Vt.) endorsed Mamdani and said his victory represents the change that the Democrat party needs and urged Democrats to follow his lead.
"In many ways, Mamdani’s campaign really shows the direction in which the Democratic Party should be moving," Sanders said. "And that is not to worry about what billionaires want, but to worry about what working-class people want.
"People like Mamdani are [the GOP's] worst nightmares. It’s one thing for the Democrats to be strongly against Donald Trump. It is another thing to give working class people something to vote for—a positive agenda."
Notably, the top two Democratic leaders in Congress, Sen. Chuck Schumer and Rep. Hakeem Jeffries, declined to endorse him.
If elected, Mamdani would be the city’s first Muslim and Indian American mayor.
Incumbent Mayor Eric Adams was elected as a Democratic but will run for re-election in November as an independent. Cuomo is deciding if he will stay in the race under his registered Fight & Deliver ballot line.
Curtis Sliwa, a radio talk show host and founder of the Guardian Angels, automatically became the official GOP candidate for the general election without a primary after running unopposed in the Republican race in the deep blue city.