There was a picture of Lenin tacked on the wall, a shelf of books about Che Guevara and a cafe serving avocado toast.

The young true believers and rickety old militants in attendance were learning history and strategy from Frances Fox Piven, a distinguished professor of political science at the Graduate Center of the City University of New York.

“Since the 1970s, everything has gotten worse and worse,” said Piven, 86. There were very clear reasons for this. “Poor people,” she said, had been “humiliated” and “shut up.” Those in power now are “crazy.”

“But they’re also evil,” she continued. “And they will be evil because they are greedy.” Only one thing would stop them, she said. “We have to be noisy, and difficult and ungovernable.”

Piven has been making this argument for over half a century. While Democratic veterans like the House speaker, Nancy Pelosi, seek to build consensus, Piven praises its opposite: “dissensus.”

Trying to work within the system is terribly misplaced, Piven argues, since it’s rigged by elites against the poor. What’s needed is a sense of crisis that will force change. And that, she insists, can be achieved only by the “mass defiance” of a disruptive protest movement.

These revolutionary ideals long made Piven infamous to some, heroic to a few and unknown to everyone else. But with the rise of a youthful radical left, her admirers are growing in influence for the first time since Piven entered politics in the 1960s.

Bookish political operatives and labor organizers in the Democratic Socialists of America — whose membership has increased by nearly 50,000 since 2015 — revere Piven.

According to David Duhalde, 34, formerly the Democratic Socialists’ deputy director and now the political director of Our Revolution, a group aligned with Sen. Bernie Sanders of Vermont, the “ideological leadership” is full of Pivenites.

Micah Uetricht, 31, managing editor of the socialist magazine Jacobin, is also devoted to Piven’s work. He said he has read “Poor People’s Movements,” Piven’s venerated 1977 book, at least three times.

“She’s someone whose body of work shows that you don’t have to drift off into this la-la land of intellectualism,” Uetricht said. “People should be going on strike. People should be withdrawing their labor power or causing chaos in society. That’s where their power comes from.”

Probably the most influential vector for Piven’s ideas is the social-justice incubator Momentum, a training program for progressives that formed in 2014.

Trainees include members of the Sunrise Movement, whose occupation of Pelosi’s office with Alexandria Ocasio-Cortez sparked conversation about the Green New Deal. It was just the sort of disruption Piven advocates.

“What tactics we use is exactly the question that Piven is addressing,” said Lissy Romanow, 35, Momentum’s executive director. Part of Piven’s appeal, she said, came from her view that social movements are required for big left-wing victories — a perspective suited to a generation disillusioned with liberal business as usual.

Piven takes an active part in spreading her own ideas. In July, she will be headlining the 2019 Socialism Conference, to be held in Chicago and sponsored by Jacobin magazine and the Democratic Socialists.

For decades, no event has struck her as too small.

Before the Democratic Socialists of America had its resurgence in 2016, the organization would hold summer youth retreats in upstate New York. A few dozen college students would attend lectures and discussions, taking breaks for games of whiffle ball and bonfires. Piven always came. “She was a celebrity showing up to these embarrassing meetings,” Duhalde said.

“I’ve seen Fran at organizing meetings, I’ve seen her at protests, at Occupy, at conferences, retreats and planning sessions,” said Sarah Jaffe, 38, a left-wing journalist and author. “She’s obviously one of the most influential people I can think of.”

Piven was born in Canada in 1932 and grew up in Queens. Her parents both emigrated from Uzlyany, a shtetl near Minsk.

It’s a background shared by other great polemicists of the 20th century. Sociologist Nathan Glazer, historian Howard Zinn and writer Vivian Gornick also were born between 1920 and 1935 to Jewish immigrant parents from Eastern Europe and grew up in outer-borough New York. The same goes for socialist critic Irving Howe, whose father, like Piven’s, struggled to run a deli.

Secular to the point of not celebrating birthdays, nostalgic for the culture of Russia and bitterly conscious of their poverty, Piven’s family found a source of meaning in politics. This was most true of her father.

“He told me a little bit about capitalism, how it’s a dog-eat-dog society, and that you couldn’t believe the capitalist press, it was all full of lies,” Piven said. “I said, ‘Why do you read the newspaper, Daddy?’ Because he read it — he really read it. And he said, ‘I read between the lines.’ Being literal-minded as little kids are, I tried to do that. I tried and tried.”

Rebelliousness came to her early. In elementary school, she refused to say the Pledge of Allegiance, even after being forced to stand in a corner with her face to the wall. “I said I could only pledge allegiance to the Maple Leaf,” Piven recalled. “I was a Canadian.”

In 1962, she started working at Mobilization for Youth, the New York anti-poverty program that became a model for President Lyndon Johnson’s War on Poverty. Soon, she was observing rent riots and watching speeches by figures such as Malcolm X. She said that once, while standing guard outside a student-occupied building at Columbia University, she was attacked by police.

During the welfare rights movement of the late ’60s and early ’70s, Piven repeatedly stormed welfare centers with other activists to demand benefits — including on her birthday, which led to her arrest. “Know what he said?” asked Piven, recalling her talk with the policeman. “‘You must be a very nice person to do this on your birthday.’”

All of these experiences showed Piven the art and power of political confrontation. “The streets of New York, the streets of the Lower East Side, the streets of Harlem — you could feel the energy almost crackling,” she said of her early days in politics. “That assertiveness came with anger, and a certain violence.”

Following the crucible of the ’60s and early ’70s, Piven’s academic career flourished. Her books, particularly “Poor People’s Movements,” were assigned in college classes. She received awards and held prestigious posts: honorary chairwoman of the Democratic Socialists of America; vice president of American Political Science Association; president of the American Sociological Association.

At the same time, politics no longer fully accommodated her desire for fiery activism. Piven helped lead a successful drive to reform voter registration, but it was a campaign that rested on tactics tamer than “mass defiance.” During academic conferences and at least one televised debate of the 1990s, Piven became a lonely advocate for welfare rights as much of the country turned against the welfare system.

Her public profile came to rest, perversely, on attempts of right-wing commentators to tar moderate liberals with her brand of radicalism. Television personality Glenn Beck repeatedly identified Piven and her husband and collaborator, Richard Cloward, who died in 2001, as a secret, dark force, “fundamentally responsible for the unsustainability and possible collapse of our economic system.”

This style of condemnation continues. A recent article on the political news site RealClearPolitics claimed that “all social policy innovations since the 1960s have been incremental steps in the Cloward-Piven plan to bankrupt America.”

Without quite thinking she is a wicked witch of the left, liberals have still strongly objected to many of Piven’s views. John McWhorter, a writer and linguist, for example, argued that Piven and Cloward’s work on welfare rights led African Americans to become dependent on welfare.

The division between Piven and other supporters of the Democratic Party comes in part from the fact that while most changed their views over time, Piven did not.

Sean Wilentz, a professor of American history at Princeton University, was once a radical in the vein of Piven. As a young man, he attended the tumultuous protests surrounding the 1968 Democratic National Convention and felt pushed toward militancy. Then, like many other members of his generation, he grew disillusioned with what he saw as dogma and destructiveness and found there was greater power in America’s tradition of liberal reform.

In an interview, Wilentz said he disputed the moral implications and efficacy of Piven’s tactics.

Piven’s promotion of mass disruption rests on the idea that it deserves credit for the biggest progressive achievements in American history. Abolitionists, she argues, brought about emancipation, while jobless protesters and striking workers forced the most progressive legislation of the New Deal.

Wilentz disagrees.

“It’s not true that social movements are everything and politicians are just these ciphers,” he said.

When disruption has become divisive or violent, Wilentz said, it has invited backlash. “The legacy of the more riotous protests we’re talking about is Donald Trump,” he said.

Moderate Democrats worry a strident style will similarly doom today’s ascendant left.

Piven responds to such criticism by arguing that backlash is an inevitable consequence of righteous political campaigns. Most violence associated with protest, she observes, comes from authorities suppressing demonstrators.

“People do get hurt,” she acknowledged matter-of-factly. After continued probing, Piven finally found a movement she could describe as going too far. “I think the French Revolution was awful,” she said.

Today, Piven lives in a spacious, simply furnished apartment near Columbia University, where she moved with Cloward in 1983. She still ventures out to meet with activists and to deliver public speeches as often as possible, but she recognizes she is growing frail. Piven often prefers to see friends and students in her apartment, where she likes to wear a cozy sweatshirt of the Green Bay Packers — the football team whose public ownership some consider quasi-socialist.

Young people seem drawn to Piven, and she occasionally writes with younger colleagues, deploying the edgy imagination of what she once called “the strategist of dissensus.”

In a recent interview with Jacobin, she wondered about the possibility of disrupting supply chains by closing truck depots along the New Jersey Turnpike. She frequently mentions her wish for a mass movement to renege on debt payments. Perhaps people would be inspired to protest the unjust economic conditions that force them into debt, she thinks, if school boards challenged exploitative loans they’d received from banks.

“You can’t be Frances and sit quietly in an armchair,” said Barbara Ehrenreich, the distinguished left-wing author, who is an old friend of Piven’s. “When people are marching in the streets, Frances has got to be out there with them.”

Much as Piven upholds defiant protest as the path to leftist victory, she also clearly takes pleasure and pride in the act of confrontation itself. She happily remembers, for instance, the campaign she was part of in the 1970s and ’80s to remove John Silber, the controversial president of her former employer, Boston University. So what that the movement failed?

“Working on any political project is enormously fun,” she said. “You don’t have to win for it to be really terribly satisfying. You get good friends. You do the right thing. You test your courage.”