New York elected Zohran Mamdani as its next mayor on Tuesday as Democrats also won two key state governor races, with US voters delivering an early warning to President Donald Trump ahead of the 2026 midterms.

Democrats swept the top contests across several ballots nationwide, boosting the party after Trump’s return to the White House and raising concern among Republicans.

Mamdani won despite attacks on his policies and Muslim heritage from business leaders, conservative media and Trump.

In a victory speech to supporters Mamdani said: “If anyone can show a nation betrayed by Donald Trump how to defeat him, it is the city that gave rise to him. In this moment of political darkness, New York will be the light.”

Democratic victories in the governor races in Virginia and New Jersey pointed to a shift as the country heads towards next year’s midterm elections, when control of Congress will be contested.

Voters in California also approved a proposition to redraw electoral districts to counter gerrymandering efforts ordered by Trump in other states.

Trump rejected any responsibility for Tuesday’s results. On Truth Social, he cited unnamed “pollsters” who suggested Republican losses were due to the government shutdown and the absence of his name on ballots.

House minority leader Hakeem Jeffries wrote on X that “Democrats are smoking Donald Trump and Republican extremists throughout the country,” adding that “the Democratic Party is back.”

Mamdani, a state lawmaker from Queens, campaigned on tackling the cost of living, free bus travel, childcare and city-run grocery stores.

He focused on living costs for New Yorkers, building support through his personal style, social media and a large canvassing effort.

“The next and last stop is City Hall,” Mamdani said in a video posted to X after his win.

The self-described socialist was little known before defeating former governor Andrew Cuomo for the Democratic nomination, and he beat him again on Tuesday.

Supporters gathered at a Brooklyn concert venue to watch the results.

Trump intervened late in the race, calling Mamdani, who will become New York’s first Muslim mayor in January, a “Jew hater.”

Republican Curtis Sliwa, founder of the Guardian Angels, finished third after Cuomo urged him to exit the race to boost his own chances.

Business figures including Bill Ackman criticised Mamdani and funded his opponents, while conservative media such as The New York Post ran negative coverage.

Turnout was high, with 1.45 million ballots cast by 3 pm, exceeding the total number of voters in the 2021 election.

London’s mayor drew parallels with his own political success when he celebrated Mamdani’s victory, while also appearing to take a swipe at US President Donald Trump and his own mayoral predecessor Boris Johnson.

Sir Sadiq wrote in a post on X: “New Yorkers faced a clear choice – between hope and fear – and just like we’ve seen in London – hope won.” He added: “Huge congratulations to @ZohranKMamdani on his historic campaign.”

The two mayors appear to have some common ground: Both are social democrats and have each made history as the first Muslim mayors of London and New York.