"Donald Trump, since I know you’re watching, I have four words for you: turn the volume up!" Mamdani, a Democrat, said during a Tuesday night speech to a raucous crowd of supporters shortly after being declared the victor.

Democrats swept a trio of races on Tuesday in the first major elections since Trump returned to power nine months ago, elevating a new generation of leaders and injecting fresh momentum into the beleaguered party ahead of next year's congressional elections.

Mamdani made countering the 79-year-old Republican president's actions in the city -- especially on immigration -- a centerpiece of his campaign. The next three years will test his ability to go toe-to-toe with Trump, who wields the world's biggest bully pulpit and thrives on bare-knuckle politics.

Trump has repeatedly turned the massive powers of the presidency on political rivals, and already before the election had threatened to possibly withhold billions of dollars in federal funding from New York City if Mamdani, a democratic socialist, was elected. This would follow previous funding cuts by the Trump administration in political moves targeting Democratic congressional leaders also from the city.

"If you have a communist running New York, all you're doing is wasting the money you're sending there," Trump told CBS' 60 Minutes on Sunday, previewing how Republicans will use Mamdani's embrace of a socialist agenda as a line of attack against the Democratic Party.

Mamdani acknowledged his win poses a challenge implementing what he calls "the most ambitious agenda to tackle the cost-of-living crisis this city has seen” since the 1940s -- including a proposed rental freeze, universal childcare and other government actions targeting the private sector.

"So hear me, President Trump, when I say this: To get to any of us you will have to go through all of us," Mamdani added.