A man or a movement? That was the question being asked when Zohran Mamdani gambled his political capital on Tuesday’s elections in New York.

The answer from voters was emphatic: they prefer Mamdani and his brand of democratic socialism to the Democratic party establishment and its lukewarm version of capitalism. America’s biggest city has swung even further to the left.

The New York Knicks might have won in five, but Mamdani did it in three. The mayor audaciously backed a trio of candidates in Democratic primaries for the US House of Representatives, and all three prevailed over establishment-backed rivals. Two were fellow democratic socialists.

Most dramatically, Adriano Espaillat – the chair ​of the Congressional Hispanic Caucus – lost his bid for reelection to Darializa Avila Chevalier, a democratic socialist who has not held public office before, and once wrote “Fuck Kamala Harris” on social media.

In the primary for retiring congresswoman Nydia Velázquez’s seat, state assembly member Claire Valdez beat Brooklyn borough president Antonio Reynoso. Valdez was endorsed by Mamdani, while Reynoso was endorsed by Velázquez.

A third candidate backed by Mamdani, former city comptroller Brad Lander, defeated congressman Dan Goldman – a former federal prosecutor who served as lead counsel for Trump’s first impeachment – in a landslide by running to his left. Lander criticised the support by American Israel Public Affairs Committee (Aipac) of Goldman, and promised to sponsor legislation that would put restrictions on military aid to Israel.

The results demonstrated that Mamdani has lost none of his political magic. He took a risk by intervening in the congressional races, alienating some Black and Latino Democrats and trade unions along the way, but it paid off handsomely.

The mayor-turned-kingmaker had said it was a question of electing “better Democrats” who would “put working people back at the heart of politics”. All three victors are expected to win their safely blue districts, which would send three Mamdani allies into Congress next January.

The outcome was also a recognition of some wider trends in US politics: socialism is no longer a dirty word, criticism of Israel is no longer taboo and dissatisfaction with Democratic leaders in the Donald Trump era runs deep. Voters are thirsty for energy, fight and fresh ideas.

They ask: if Republicans can draw up a Project 2025 and pursue it ruthlessly, why can’t Democrats come up with a Project 2029 that promises universal healthcare, supreme court reform, massive climate investments, a war on the oligarchs and a clear-eyed approach to the Israeli prime minister, Benjamin Netanyahu?

A decade after Bernie Sanders’ insurgent presidential campaign rattled the status quo, something is shifting. A Gallup survey last year found that only 42% of Democrats view capitalism favourably while 66% have a positive view of socialism.

On Tuesday night, a crowd greeted Mamdani with chants of “Free, free Palestine” and “DSA!” – the initials of the Democratic Socialists of America. The results in New York came after democratic socialist mayoral candidates won the Democratic primary in ⁠Washington DC and made the runoff in Los Angeles.

Voters have been sending a message to Democrats: stand for something, rather than nothing, because writing strongly worded letters to Trump is not enough. They regard Congress as lethargic and ineffective against the authoritarian onslaught, in contrast to the energy of Democratic governors and mayors.

Many were incensed by Biden and Harris’s backing of Israel’s war in Gaza, which resulted in more than 73,000 Palestinian deaths, after a Hamas-led attack in 2023. Some were frustrated by a Democratic National Committee election autopsy that pulled punches and failed to mention Gaza at all.

A significant number voters are also sceptical of Chuck Schumer, the Senate minority leader, and Hakeem Jeffries, his equivalent in the House, both New Yorkers and staunch supporters of Israel. Schumer declined to endorse Mamdani before the mayoral general election, while Jeffries only did so 11 days before polling day. Jeffries had supported Espaillat and Goldman on Tuesday, but voters delivered a rebuke reminiscent of the Tea Party that once shook Republicans.

Van Jones, a political commentator and former official in the Barack Obama administration, told CNN: “This is a battle between the establishment and this insurgency. And the roof is collapsing on the Democratic party establishment tonight … This is no longer a movement; this is a movement and a machine at the same time.”

There were some consolations for the establishment. Victories for the moderates Ben McAdams in Utah, and Cait Conley in the suburbs of New York, were a reminder that this will be a team effort – and the House majority – will be decided in swing districts in November. Democrats hope their divisions will be papered over by fierce anti-Trump sentiment.

But once the midterms are done, Mamdani and his allies will be a powerful force in determining the Democratic presidential nominee in 2028. That could put wind in the sails of yet another New Yorker: the progressive star Alexandria Ocasio-Cortez.

It is exactly 12 months since Mamdani beat Andrew Cuomo in his own Democratic primary, putting him on course to win the mayoralty. “A year ago, it was not the end of a political movement,” he told supporters on Tuesday. “It was the beginning.”