Zohran Kwame Mamdani won the Democratic mayoral primary last night. The socialist began this election with almost no name recognition. After his campaign left everything on the field, prepared for weeks of uncertainty and vote-counting complexity, Mamdani won so decisively last night that his main opponent, former governor Andrew Cuomo, a man who famously does not take no for an answer, conceded the race before 11 p.m.

Mamdani has moved quickly from candidate to historic phenomenon. His campaign and personality give New Yorkers hope. Speaking to a union crowd on the sidewalk at a poll site near Union Square yesterday, as temperatures climbed toward 100 degrees Fahrenheit, a beaming Mamdani, gamely wearing a “United Auto Workers for Zohran” T-shirt over a dress shirt, seemed to hardly break a sweat as motorists slowed their cars, honked their horns, and snapped pictures on their phones.

His victory is the biggest one yet for a socialist movement that has been building support steadily in New York City ever since Bernie Sanders ran for president in 2016. New York City’s Democratic Socialists of America (NYC-DSA) chapter, along with neighboring partners like Mid-Hudson Valley DSA, has won elected offices and legislative reforms, expanding renters’ rights, taxing the rich, and building publicly funded renewable energy, but before Mamdani’s campaign, had yet to become a mass movement.

The candidate is charming and surrounded by media geniuses. But more than anything, organizing — more than 40,000 volunteers — made this happen. And that organizing can’t be separated from the socialist vision that animates it.

That vision is big: a city that working-class New Yorkers could afford. At the same time, it’s specific: rent freezes; fast and free buses; affordable housing; a public option for groceries; and a clear commitment to public safety, investing in mental health responders for people in crisis, allowing police to focus on preventing and solving serious crimes.

This was a straightforward triumph of people over money, the kind that capitalist elites try so hard to convince is impossible. Cuomo’s campaign was bankrolled by $25 million from some of the worst actors in American life — more than $8 million from billionaire and former New York City mayor Michael Bloomberg; $2.5 million from a landlord group; $1 million from DoorDash, a food delivery app deeply dependent on the exploitation of low-wage workers; and half a million from Bill Ackman, a Trumpist hedge funder who has been attempting to destroy the campus Palestinian solidarity movement (and with it, all of American higher education) — in total comprising the largest super PAC in the history of New York City mayoral campaigns. Mamdani didn’t just beat money as usual, he beat an extraordinary mobilization of money.

Mamdani’s campaign shows that much of the canned conventional wisdom that consultants serve up to the Democratic Party is nonsense. Conventional politics decrees that door-knocking doesn’t work, that young people won’t vote no matter how hard you try to turn them out, that certain demographics (white men, very religious voters) are immutably conservative. And ever since Bernie Sanders inspired so many but did not become president, centrist Democratic leadership has insisted that improving people’s material conditions cannot form the basis of a winning politics. Mamdani’s victory shows they’re wrong about everything.

Mamdani’s victory also proved the Democratic establishment spectacularly wrong on Israel. The candidate who vowed to arrest Benjamin Netanyahu for war crimes if he came to New York, who wouldn’t agree to visit Israel if elected, beat Netanyahu’s lawyer. For his commitment to solidarity with Palestinians and opposition to the genocide, the candidate was constantly tarred as an antisemite by Israel’s apologists.

If anything, all those attacks seemed to actually help Mamdani, by letting voters know that he opposed the war in Gaza and refused to back away from a principled stance out of supposed political expediency. This victory shows that we’re moving into a political environment where, with enough organizing and frank explanation, people see that criticism of Israel is not toxic: it’s Israel itself that is toxic. Two progressive city council members in Brooklyn, Shahana Hanif and Alexa Avilés, were targeted by pro-Israel forces for their sympathy with Palestine; both handily won reelection last night.

The general election is going to be wild. While it’s unclear whether Cuomo will decide to stay on the ballot — being routed in the primary, he seems to be rethinking that plan — Mamdani will still face disgraced but determined incumbent Mayor Eric Adams and Republican Curtis Sliwa. The establishment will certainly try hard to defeat Mamdani in November.

If Mamdani does become mayor, the mass movement that elected him must be prepared to help him succeed, as the ruling class (especially the real estate industry), the Trump administration, and the police make every effort to make his mayoralty a failure. He will face much more pressure to succeed than ordinary mayors, to be able to stand up against backlash; he will need to appoint the most experienced team, drawing on the existing rich expertise of the city’s most dedicated civil servants.

He will need to work tirelessly not only on fulfilling his campaign promises but on issues that matter to the middle class, like K-12 education and cleanliness. Under austerity mayor Adams, we have had to step nimbly over human excrement on the stairs as we exit subway stations. Under a Mayor Mamdani, that same pile of excrement could easily become a symbol of why socialism doesn’t work. He needs to demonstrate that socialism — much more so than neoliberalism — can keep the shit off the steps.

Mamdani, NYC-DSA, and the broad New York City left have accomplished the hardest thing in American politics: convincing people that change is possible. When you talk to most people about socialist or social democratic ideas — from single-payer health care to free buses — they usually don’t dislike those ideas, they just don’t believe any of that can happen. This campaign showed that it can.