Was it Opposite Day at Liberty University? Here was Bernie Sanders, who spent his 20s preaching sexual liberation and social revolution, taking the stage to speak to a student body of fresh-faced Christian conservatives at the school founded by televangelist Jerry Falwell. Liberty students pay a $25 fine for “attendance at a dance” and $50 for “visiting alone” off campus with a member of the opposite sex. At 74, Sanders was an old man among young people, a self-described “democratic socialist” in the boiler room of the Christian right. And you could argue that his presence was the opposite of clever. After all, why was this overachieving underdog of the Democratic Party–the breakout star of a season that was supposed to be all about Hillary–stumping for votes in a place where he had virtually no chance of finding them?

Why does a missionary venture out among the heathen? Bernard Sanders, a paint seller’s son from Flatbush, an early-’60s campus radical, a rumpled transplant to progressive Vermont who worked his way gradually up a small ladder in a small state to become the unlikely embodiment of a very large yearning–leads with his heart and his sermons. He seeks conversions, not just votes.

If that strikes you as insufficiently calculating, you are starting to understand Bernie’s momentum. And to understand the Sanders surge is to understand the spirit of 2016. Look around at the candidates who are stumbling and fumbling toward the first balloting less than five months away. Republican Jeb Bush of the White House Bushes learned to count delegates when most kids were still counting fireflies. Democrat Hillary Clinton is part of a family that once commissioned a poll to choose a family vacation that would endear them to voters. So far, calculation is getting them nowhere. The surging candidates–rampant Donald Trump, novice Ben Carson and retro Bernie Sanders–represent the opposite. Slickness is out, conviction is in.

“I am not a theologian. I am not an expert on the Bible,” Sanders told the crowd of 13,000 at Liberty. “I am just a United States Senator from the small state of Vermont.” With that caveat, Sanders painted scenes of a progressive utopia: free higher education, health care for all, bolstered wages and chastened billionaires. The audience in Virginia received him politely, though their biggest wave of applause went to the student who asked why his compassion for the weak did not extend to unborn babies. Sanders’ real audience–the roughly 1 in 4 Democratic-primary voters who have lifted him into contention against former Secretary of State Clinton–could only love him more than ever. He was defending the faith. Daniel, as they might put it at Liberty U., in the lion’s den.

With each twist and wrinkle of this election season, which is as wide-open and unscripted as any presidential cycle in living memory, we see more clearly that these are special times in American politics, baffling times, times to challenge categories and scramble expectations. The Internet has killed the kingmakers. Freshness beats incumbency, while the perception of sincerity beats all. There is no room for focus groups in the elevator to the top of the polls; America wants its candidates straight up and packing a kick. This is how a squinty-eyed New Yorker goes from shooting his cuffs and hawking condos to the head of the GOP pack. It’s how Bernie Sanders can join the Democratic Party in April and by August be battling for first place in Iowa and New Hampshire.

Without a single TV ad–or a single congressional endorsement–Sanders has exposed the weakness of the party’s Clintonian establishment while at the same time spotlighting its hunger for an ideological savior. Polls now indicate that if the nominating contests were held tomorrow, Sanders would edge out Clinton in Iowa and beat her in New Hampshire by 10 points. Nationally, he has cut Clinton’s lead from an impregnable 46 points to a crumbling 21 points in just two months.

But even those metrics don’t convey the extent of the Sanders phenomenon. At Clinton events, campaign staffers section off floor space before her speeches to make her crowds look densely packed. Sanders needs no barriers. His audiences are authentically huge–28,000 in Oregon, 11,000 in Arizona, 7,500 in Maine. His volunteer army, meanwhile, though mostly self-organized online, numbers more than 182,000 people spread out from rural Alaska to the Florida Keys, people who have asked the campaign how to improvise events, knock on doors and spread the gospel from campus quad to living room to farmer’s market.

Win or lose, Sanders seeks to transform his party and redeem American politics through an epic battle against some of the wealthiest powers in human history. “A lot of people have given up on the political process, and I want to get them involved in it,” he tells TIME. “In this fight we are going to take on the greed of the billionaire class. And they are very, very powerful, and they’re going to fight back furiously. The only way to succeed is when millions of people stand up and decide to engage.”

This is not just a campaign, says Sanders. It is a “movement,” a “revolution.” He is not only after delegates; he plans to “raise the political consciousness.” Contrast this with the message Clinton conveyed during a meeting this summer with a group of activists. Consummate political engineer, virtuoso of the knobs and dials of public opinion, Clinton said, “Look, I don’t believe you change hearts. I believe you change laws, you change allocation of resources, you change the way systems operate.” David Axelrod, the onetime guru to Barack Obama, brutally mocked the plodding story line. “Hillary: Live With It,” tweeted Axelrod, “is no rallying cry.”

Sanders is all rallying cry. When the Wall Street Journal attempted to tally the cost of his agenda–trillions in new government spending on health care, 90% tax rates on the superwealthy, free public college, a Scandinavian-style safety net–his defenders criticized the effort. It’s time, Sanders says, for billionaires storing their cash in the Cayman Islands to pay up. He is tapping into a recurring desire among Democrats for an outsider to purify the party. “Carter, Clinton and Obama all ran against the party,” Simon Rosenberg, Democratic strategist and veteran of Bill Clinton’s 1992 campaign, observed of the last three Democrats to reach the Oval Office. “We don’t do coronations. It’s not our thing.”

What better way to convey his purity than to take his message to Liberty U., where abortion is murder and gay marriage apostasy. “We are living,” Sanders told the students, “in a nation and in a world which worships not love of brothers and sisters, not love of the poor and the sick, but worships the acquisition of money and great wealth. I do not believe that is the country we should be living in.”

For Phil Boyd, the revolution began in August, when the 24-year-old manager at Barnes & Noble started marching door to door in his town of Clayton, N.J., seeking Sanders recruits. Within weeks, he decided to drive six hours to New Hampshire to hear the firebrand in person.

Sanders delivers stump speeches that are equal parts economics and jeremiad. His numbers have an apocalyptic feel: the 15 wealthiest people in America saw their net worth grow $170 billion in the past two years; 99% of all new income today goes to the wealthiest 1%. Meanwhile, the earth trembles in the face of global warming–“more drought, more floods, more extreme weather disturbances, rising sea levels,” Sanders preaches. “It means more acidification of the ocean with calamitous impact on mammal life.”

What Boyd really wanted, though, came after the fire and brimstone. “Yes, I am here,” Sanders told the crowd in his gravelly Brooklyn accent. “I want to win the Democratic nomination. But I need something more than that–I need your support the day after the election.” Like many others who are rallying to Sanders, Boyd was seeking more than a candidate. He wanted a cause for the long haul. “We have to keep our foot on the pedal, whether it’s Bernie or anybody else who wins,” Boyd said.

Truth be told, many Sanders supporters would have preferred a fresher standard bearer to expose the injustice of income inequality and rail against the buying of elections. Senator Elizabeth Warren of Massachusetts comes to mind. But Berniemania is about more than just the candidate, and more than one election. “The end goal is to build a political movement that pushes beyond whatever the campaign is or does,” says Corbin Trent, a 35-year-old who sold his food-truck business in Tennessee and now travels the state on behalf of the movement.

Such stories of abandoning careers and setting aside studies to join the Sanders brigades are common. Stephanie Rountree, a 17-year-old high school senior in Baltimore, spends upwards of 20 hours a week analyzing data and helping train volunteers. In Concord, N.H., palliative-care doctor Bob Friedlander left medicine to volunteer full time, rallying health care workers. Alayna Josz, a manicurist in nearby New London, N.H., paints red, white and blue Bernie slogans on her customers’ nails. “He says the things I always wanted to hear, that I knew were true,” Josz, 27, gushes. “All day long, I find myself thinking about Bernie and this revolution.”

The challenge Sanders faces is to build a campaign that can harness this energy effectively. His paid staff is growing rapidly, from four to nearly 40 in New Hampshire in just a month’s time. In Iowa, Sanders is quickly catching up to Clinton, with 54 paid staff to her 78 organizers. He’s set his sights on hiring in the Super Tuesday states.

He has volunteers eager to be involved in 47 states from Alabama to Michigan, where the campaign has no staff and no offices. In a largely unproven experiment, two staffers at the Burlington, Vt., headquarters are using conference calls, Internet chats, organizing parties and digital seminars to train hundreds of Sanders enthusiasts–who in turn are supposed to train other volunteers in rippling circles of self-sufficiency.

The results so far have been unpredictable. Over 100,000 people have said on Facebook that they would attend an “Enough Is Enough” rally on the Washington Mall to support Sanders. But the campaign hasn’t sanctioned the event. In San Antonio, 50 Sanders acolytes picketed a prominent Clinton backer–which came as a surprise to Sanders when he read about it in the newspaper the next day. “Sometime, I’m sure we’ll get in trouble because one of these groups will say something we’ll have to disavow,” Sanders tells TIME.

We’ve seen this movie before: a grassroots darling surges to early stardom only to lose to a better-organized moderate. In 2003, the Sanders role was played by progressive Democrat Howard Dean, another Vermonter, who attracted huge crowds and an avid Internet fan base but failed to win a single nominating contest. Republican Ron Paul in 2011 drew partisans so sincere that many quit their jobs to volunteer for him, but he was just a blip in the Republican primary race.

“The whole notion of self-organizing is a pipe dream,” says Marshall Ganz, a Harvard-based adviser to both the Dean and Obama campaigns. “One of the great values of the Internet is it’s a way to share information, but it’s not a substitute for relational structure and accountability.”

Sanders is undeterred. There must be a way to make it work, he muses on a warm afternoon shortly after Labor Day as he slouches on a sofa in his Capitol Hill office. A poster-board cutout of a happy Holstein stands sentinel and pastoral scenes from the Green Mountain State line the walls as Sanders talks about the power of the presidency.

It’s all about the movement, Sanders admonishes in the deep bass voice that he reserves for one-on-ones. What President Obama didn’t understand when he took office is that you have to keep your movement alive. “Barack Obama ran one of the great campaigns in American history. The biggest mistake he made is that the day after the election, in so many words, he said, ‘Thank you very much, but I will take it from here,'” Sanders says.

Then he paints one of his word pictures. Imagine President Sanders facing a vote in Congress on free college tuition paid for by a tax hike on the wealthy. He’d have to persuade Speaker of the House John Boehner to help him pass the bill. That’s where his army of activists comes in. “How do I convince John? Is my personality that much better than Barack Obama’s?” Sanders says. “The answer is to say, ‘Hey, John, take a look out your window. Because there are a million young people there that are in support of the legislation. They are voting. They know what’s going on. If you refuse to make college affordable, they’re going to vote your people out of office.’ That’s the offer you can’t refuse.”

This kind of insurgent idealism has driven Sanders all his life. His education began at home, in a 3½-room apartment in Brooklyn’s Flatbush neighborhood, which stamped his character as well as his accent. His father, the paint salesman, was a Polish immigrant and high school dropout, and the family lived paycheck to paycheck. Teenage Bernie studied Karl Marx and Greek democracy with his older brother, who brought him to neighborhood Democratic Party meetings. When his mother died unexpectedly, Sanders fled New York for the University of Chicago, where he threw himself into activism. By his 23rd birthday, Sanders had worked for a packinghouse union, joined Martin Luther King Jr.’s March on Washington, signed up with the university socialists and been arrested at a civil rights demonstration. He was a sloppy student but an ardent radical of the sweater-and-slacks, nonviolent early-1960s variety.

In his second year at college, Sanders made national news. One frigid Tuesday in January 1962, the 20-year-old stood on the steps of the administration building and railed in the wind against the college’s housing-segregation policy. “We feel it is an intolerable situation when Negro and white students of the university cannot live together in university-owned apartments,” the bespectacled Sanders told a few dozen classmates. Then he led them into the building in protest and camped the night outside the president’s office. It was the University of Chicago’s first civil rights sit-in, and a first taste of victory for Sanders.

From there he made his way to Burlington, Vt., where he staged unsuccessful bids as a socialist candidate for governor and Senator in the 1970s. His winning campaign for mayor of Burlington in 1981 was a notable counterpoint to Ronald Reagan’s conservative uprising, and it launched Sanders on an upward trajectory that took him to Congress in 1991 and the Senate in 2007.

Now, as most of his Kennedy-era comrades have faded from the scene, Sanders has become ubiquitous in Democratic politics–to the irritation of the front-running Clinton. At a recent event in Iowa, for example, a student fired his name at Clinton like a spitball. “Hi, I really wanted to ask about your political views for Bernie Sanders?” a young man clumsily asked at his earliest opportunity. “My political views?” Clinton parried. Then she dodged–a bad habit to have this year. “I don’t have any issue whatsoever in having a really good, strong contest for the Democratic nomination,” she said.

Clinton’s aides say they prepared for a strong challenger and they’re not changing course. The insurgent has been unable to break through with African-American voters, who could prove decisive in the later primaries. “Sanders may be rocking her with white progressives,” says Joe Trippi, a veteran Democratic strategist. “His problem is whether he can break Clinton’s domination of minorities. It’s a huge hurdle if it can’t be solved.” Clinton is still far ahead in nationwide polls, leading Sanders by around 20 percentage points. And her minions have begun to attack, sending out fact sheets that draw comparisons between Sanders and former Venezuelan ruler Hugo Chávez. “That is the kind of politics that I’m trying to change,” Sanders says of team Clinton’s attack.

Characteristically, Sanders professes to be uninterested in such details. “This campaign is about begging you to fight for your kids and your parents, to fight for your planet, fight for the future of your country,” he says. There is no calculation in that answer. Let the other candidates worry about the horse race; Bernie Sanders is worried about forever. It is the opposite of everything we’ve come to expect from the political process–and this year, being an opposite is the secret to success.

This appears in the September 28, 2015 issue of TIME.

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