At 68, Jeremy Corbyn has been on the Labour Party’s left flank longer than many of his most enthusiastic supporters — the ones who nearly propelled him to an upset victory in this month’s British general election — have been alive. Bernie Sanders, who won more votes from young people in the 2016 primaries than Donald Trump and Hillary Clinton combined, is 75, and has a demeanor that, honestly, reminds me of my Jewish grandfather. Jean-Luc Mélenchon, the Communist-backed candidate who, thanks to support from young people, surged in the polls ahead of the first round of France’s presidential election, is a sprightly 65.

What has driven so many young people into passionate political work, sweeping old socialists with old ideas to new heights of popularity? To understand what is going on, you have to realize that politicians like Mr. Sanders and Mr. Corbyn have carried the left-wing torch in a sort of long-distance relay, skipping generations of centrists like Bill Clinton and Tony Blair, to hand it to today’s under-35s. And you have to understand why young people are so ready to grab that torch and run with it.

Both Britain and the United States used to have parties that at least pledged allegiance to workers. Since the 1970s, and accelerating in the ’80s and ’90s, the left-wing planks have one by one been ripped from their platforms. Under Mr. Blair, Labour rewrote its famous Clause IV, which had committed the party to the goal of “common ownership of the means of production, distribution and exchange.” Under Mr. Clinton, the Democratic Party cut welfare programs and pushed anti-worker international trade deals. Writing in 1990, Kevin Phillips, a former strategist for Richard Nixon, called the Democrats “history’s second-most enthusiastic capitalist party.” Elsewhere in Europe, traditional socialist parties became sclerotic and increasingly business-friendly.

All of this left many voters with a sense that there is no left-wing party devoted to protecting the interests of the poor, the working class and the young.

Meanwhile, people my age — I’m 29 — are more in need of a robust leftist platform than ever. The post-Cold War capitalist order has failed us: Across Europe and the United States, millennials are worse off than their parents were and are too poor to start new families. In the United States, they are loaded with college debt (or far less likely to be employed without a college degree) and are engaged in precarious and non-unionized labor. Also the earth is melting.

There’s nothing inherently radical about youth. But our politics have been shaped by an era of financial crisis and government complicity. Especially since 2008, we have seen corporations take our families’ homes, exploit our medical debt and cost us our jobs. We have seen governments impose brutal austerity to please bankers. The capitalists didn’t do it by accident, they did it for profit, and they invested that profit in our political parties. For many of us, capitalism is something to fear, not celebrate, and our enemy is on Wall Street and in the City of London.

Because we came to political consciousness after 1989, we’re not instinctively freaked out by socialism. In fact, it seems appealing: In a 2016 poll conducted by Harvard, 51 percent of Americans between 18 and 29 rejected capitalism, and a third said they supported socialism. A Pew poll in 2011 showed that the same age bracket had more positive views of socialism than capitalism. What socialism actually means to millennials is in flux — more a falling out with capitalism than an adherence to one specific platform. Still, within this generation, certain universal programs — single-payer health care, public education, free college — and making the rich pay are just common sense.

At the ballot box, our options have been relatively limited. Clinton- and Blair-era liberals have hobbled their parties’ abilities to confront the ills of capitalism. But while left-of-center parties ran into the waiting arms of bankers, Mr. Sanders and Mr. Corbyn held fast to left-wing politics.

In May, when Labour’s manifesto calling for free university education and increased spending on the National Health Service was leaked, Britain’s mainstream press responded with derision: “Labour’s Manifesto to Drag Us Back to the 1970s” read a headline in the Daily Mail. (In fact, some of Mr. Corbyn’s proposals, like nationalizing rail and water companies, hark directly back to Labour’s Clause IV commitments.) To some readers it may have sounded like a threat, but to many young people it was a promise. Following the headlines, Labour’s poll numbers surged. In the election on June 8, the party finished with a shocking 40 percent of the vote, its highest share in years. And much of the success was thanks to young voters.

Of course, Mr. Corbyn, who is famous for cycling to work and being “totally anti-sugar on health grounds,” has a certain ascetic charm. And there’s something appealingly unpretentious about Mr. Sanders’s Brooklyn accent and disheveled appearance. But it seems safe to say that their success with young people has been based on their platforms, not their charisma.

That’s a good thing, too, since, sooner or later, those platforms will need to acquire new representatives. America’s working class is increasingly racially diverse. Hotly contested politics around race, gender and sexuality shape our political terrain (and our experience of downward mobility). Mr. Sanders suffered shortcomings on this front: He freely confessed to not comprehending the scale of American police brutality when he began his campaign; he can sound awkward when it comes to race and gender.

The upside is that Mr. Sanders’s campaign and Mr. Corbyn’s leadership of the Labour Party have paved the way for a socialist politics that doesn’t just look like them.

The day after the election in Britain, I flew to Chicago to speak at the People’s Summit, a national convention of progressive and left-wing activists organized by people from the Bernie Sanders campaign alongside National Nurses United.

Also attending were a next generation of leftist organizers and candidates: Linda Sarsour, a 37-year-old Palestinian-American organizer from New York known for her skill in building bridges among communities; Dante Barry, the 29-year-old executive director of the Million Hoodies Movement for Justice; and Maria Svart, also in her 30s, who became the national director of the Democratic Socialists of America in 2011.

I encountered many young people who found themselves radicalized over the last couple of years and are now joining campaigns in their communities for state-level single payer health care or for better housing. Those campaigns exist because older campaigners have carried the torch. Out of all this activity, a next generation of socialist candidates who actually reflect America is almost guaranteed to emerge.

When Mr. Sanders took to the stage, I looked around to see hundreds of young organizers cheering his democratic socialist agenda. I hit the convention floor and saw people my own age tabling for new lefty magazines and organizations. A friend texted me a Corbyn emoji: thumbs up.

Three days after Britain’s general election, Mr. Corbyn sat down for an interview with Andrew Marr on the BBC. Mr. Marr grilled the Labour leader on the feasibility of turning his platform into governing policy. Was Mr. Corbyn, at this point in his career, really in it for the long haul? “Look at me!” he said. “I’ve got youth on my side.”

Originally published by The New York Times