The self-described democratic socialist was virtually unknown before his upset victory to secure the Democratic nomination over former Governor Andrew Cuomo who he trounced again today.
There was a party atmosphere at his results viewing gathering for supporters being held at a concert venue in Brooklyn, with the 34-year-old expected to speak later.
Trump made an eleventh-hour intervention in the race, calling Mamdani who will become New York’s first Muslim mayor when he takes office in January, a “Jew-hater”.
“Any Jewish person that votes for Zohran Mamdani, a proven and self-professed JEW HATER, is a stupid person!!!” the Republican President posted on his social media platform.
Curtis Sliwa, founder of the Guardian Angels citizen crime patrol group, came in third after weeks of Cuomo insisting that the Republican should bow out to increase his chances.
“It’s typical of Andrew, he’s always blaming other people for his own failures,” Sliwa told AFP ahead of the result. “Of course he’s going to blame me.”
Prominent businesspeople including Bill Ackman noisily attacked Mamdani and funnelled cash to his rivals, while conservative media including the New York Post published blanket negative coverage.
Turnout was high in this year’s vote with two million people casting ballots by 9pm.
Uphill struggle
Mamdani’s improbable rise highlights the Democratic Party’s debate over a centrist or a leftist future, with some leading national figures offering only tepid endorsements of Mamdani ahead of voting.
Cuomo said there was “a civil war in the Democratic Party”.
“You have an extreme radical left that is run by the socialists that is challenging what they would call moderate Democrats. I’m a moderate Democrat,” he said after voting.
Syracuse University political science professor Grant Reeher said ahead of the result mayor Mamdani would face an uphill battle “at the centre of all of these nasty political controversies.”
“Everybody’s got their knives out, and it’s a very difficult city to govern,” he told AFP.
“Progressives probably would have been better served if they had someone like this win a city that was easier to govern.”
In New Jersey, Democratic Party candidate Mikie Sherrill, a former Navy helicopter pilot, beat out Republican Jack Ciattarelli, a businessman backed by Trump.
In Virginia’s race for governor, Democratic candidate Abigail Spanberger unseated a Republican incumbent to beat Virginia’s Lieutenant Governor Winsome Earle-Sears.
Both sides wheeled out big guns, with former President Barack Obama rallying support for Spanberger and Sherrill over the weekend and Trump scheduling tele-rallies for both Virginia and New Jersey on the eve of voting.
Pitting centrist Democrats against Trump-aligned Republicans, both elections were seen as signalling whether middle-of-the-road voters had made peace with the President’s radical cost-slashing agenda - or plan to give his party a bloody nose in 2026.
Trump has driven a steamroller through the federal bureaucracy since returning to office in January, closing entire agencies and cutting an estimated 200,000 jobs even before the government shutdown.
Spanberger’s win in Virginia - which is second only to California in the size of its federal workforce - was no surprise, as polls had shown her holding a steady lead of seven to 12 points throughout the campaign.
The former CIA officer and three-term congresswoman was projected to beat Republican Lieutenant Governor Winsome Earle-Sears, a Marine veteran and staunch Trump ally, by a comfortable margin that makes her Virginia’s first-ever female governor.
“You all chose leadership that will focus relentlessly on what matters most - lowering costs, keeping our communities safe and strengthening our economy for every Virginian,” Spanberger said in her victory speech.
Pledge to stand against Trump
Casting herself as a bulwark against Trump’s aggressive federal downsizing, Spanberger vowed to be “a governor who will stand up” for the thousands of federal workers laid off by Trump’s Department of Government Efficiency.
Earle-Sears ran a campaign aimed at firing up conservatives, mirroring the playbook of outgoing, term-limited Republican Governor Glenn Youngkin to focus on culture war issues such as transgender athletes and abortion.
In New Jersey, Democratic former Navy pilot Mikie Sherrill was also seen as the favourite, although she was locked in a closer battle with Republican businessman Jack Ciattarelli.
The race became increasingly tight in the home stretch, with some polling showing it as a margin-of-error tussle that could go either way.
Trump’s decision to freeze funding for the Hudson Tunnel project - a vital link between New Jersey and New York - was seen as an important boost for Sherrill, who had built up a double-digit lead by the time her race was called.
On a pivotal day in US democracy, with elections at various levels of government taking place across the country, Pennsylvanians were picking new state supreme court justices while California was delivering its verdict on redistricting measure Proposition 50.
-Agence France-Presse