Zohran Mamdani barely campaigned on climate.

The New York City mayor-elect’s overwhelming focus has been on affordability, from an early ad declaring that “the cost of living is the real crisis” to his victory speech before a jubilant crowd in Brooklyn on Tuesday night. That focus didn’t stop him from winning a first-of-its-kind endorsement from a prominent climate group, the youth-led Sunrise Movement, in late April, long before he had the backing of progressive icons like Alexandria Ocasio-Cortez and Bernie Sanders.

The national group had never endorsed a mayoral candidate before, but poured its energy into the Mamdani campaign. By the time the Democratic primary arrived in June, Sunrise said its local volunteers had knocked on more than 20,000 doors in support of the candidate. They continued into the fall, and ended up knocking on about 40,000 doors, said Denae Ávila-Dickson, the group’s communications and political manager.

If President Donald Trump makes good on his threats, Zohran Mamdani may become the first New York City mayor forced to navigate an uninvited federal deployment of the National Guard. Last month, Trump insinuated that he’d send troops to “clean up” the country’s biggest city if Mamdani won the election, as he did decisively Tuesday night. Trump administration officials have also threatened to ramp up immigration enforcement raids in the city.

On the campaign trail, Mamdani, whose campaign did not respond to questions for this article, argued that he was the candidate who would staunchly defend the five boroughs from federal law enforcement. In his victory speech on Tuesday night, he welcomed a confrontation with the president.

“Donald Trump, since I know you’re watching, I have four words for you: Turn the volume up,” he said. “New York will remain a city built by immigrants, powered by immigrants. And as of tonight, led by an immigrant. So hear me, President Trump, when I say this. To get to any of us, you will have to get through all of us.”

The rhetoric matched his vow during the last mayoral debate to fight Trump “every step of the way” on immigration raids by federal law enforcement. Mamdani has also praised litigation that has limited the deployment of National Guard troops in other cities and touted a “coalition” between himself, Governor Kathy Hochul, and Attorney General Letitia James “that would be on the front lines of fighting Donald Trump.”