Like fellow movements around the world, the US Communist Party suffered a crippling blow with the collapse of the Soviet Union in 1991. But a small group of die-hard members persevered.
Not far from Wall Street, on the seventh floor of an elegant eight-storey building on West 23rd Street, is the headquarters of an improbable political survivor - the Communist Party USA.
The office is bright and modern. On one wall are black-and-white photo portraits of major figures in the party's history. The works of Marx, Engels and Lenin are stacked in bookshelves.
The building was bought to house the party in the 1970s before the surrounding neighbourhood of Chelsea became fashionable. "We got a great bargain on it," says secretary-treasurer Roberta Wood.
In a concession to capitalist reality, all but two floors are now rented out. The revenue supports People's World, an online publication that is the direct descendent of the party's long defunct newspaper, the Daily Worker.
The party claims 2,000-3,000 members nationally. It has just two salaried staff - Chairman Sam Webb and his deputy Jarvis Tyner, who was a vice-presidential candidate in the 1970s.
Its ultimate aim, however, is still sweeping in its ambition. "Socialism will usher in a new era in this country," the party programme states. "The great wealth of the United States will for the first time be for the benefit of all the people."
"The longer-term goal", says Webb, is "the communist society, the ending of all class divisions, a society of equality, the withering away of the state".
The Communist Party was once a forceful presence in American politics. In its heyday in the 1930s and 1940s it had a strong network across the country, scoring several local election successes. Three Democratic congressmen were secretly Communist Party members.
Membership never got above 100,000, but its influence was wider. "It certainly had an impact on American life," says Harvey Klehr, a political science professor at Atlanta's Emory University.
The onset of the Cold War brought persecution for US Communists and their allies, most famously at the hands of the House Un-American Activities Committee, and later, from Senator Joe McCarthy.
That period was "devastating" for the party, even though "the repression against them was so strong and over the top, it gave them a really strong sense of esprit de corps", says Vernon Pederson, professor of history at the University of Great Falls, Montana.
"It also seemed to mean to them that all the things we said were going to happen are happening - the revolution is coming and this is the first wave of repression, just like we predicted all along."
During the Cold War the CPUSA had a parallel underground structure, and a small number of people spied for Moscow. Until the 1980s the party was receiving substantial amounts of Soviet funding, says Klehr, money that the FBI knew about and tracked.
Many members left over Soviet repression in Hungary in 1956 and in Czechoslovakia in 1968, as the party maintained an orthodox, pro-Moscow line.
The final split came when Gus Hall, leader from 1959-2000, supported the coup by Soviet hardliners against Mikhail Gorbachev in 1991.
Pederson says he is "mildly amazed" the party managed to survive the fall of the Soviet Union, but credits a core of members "who simply refused to give up regardless of how bleak things looked".
"They have extremely strong beliefs and have invested an incredible amount of their own personal identities into the Communist Party," he says.
Webb, the current leader, is a slightly stooped 68-year-old with a gruff but gentle voice. He seems more comfortable talking about the current political climate than about ideology.
The immediate task, he says, is to defeat America's "extreme right" by contributing to a broader coalition of left-wing groups that campaign against economic inequality and minority rights.
The party faces a demographic challenge - a former head of the New York chapter recalls attending more than 100 funerals in the early 2000s. But it claims a small uptick in membership and payment of dues of late, attributing a surge in interest to the financial crisis of 2008 and - paradoxically - to right-wing attacks against "socialist" Democrats for piquing the interest of some on the left.
Webb points to other recent events, including the Occupy movement, the election of Socialist Kshama Sawant to Seattle's city council and Bill de Blasio winning the mayoral race in New York.
He also notes that even Republicans are talking about poverty. "The climate in the country is changing, people are thinking about economic inequality."
A socialist society is the goal in the "foreseeable future", Webb says, with communism "probably much more distant".
"If we enter coalitions on the basis of people agreeing with our vision of socialism, we could probably fit into a small but growing phone booth," he quips.
Critics who've followed the party's course, however, are dismissive.
"The positions they take are really indistinguishable from the left-wing social democratic groups," says Ron Radosh, a historian and writer who left the party after the suppression of the Hungarian uprising in 1956. "I don't even know why anyone belongs to it." Klehr calls the party "a sect, a cult almost", and says he stopped paying attention to it nearly 10 years ago because it had become "essentially irrelevant".
Tony Pecinovsky, a 36-year-old district organiser for the party in Kansas, Missouri and Tennessee, says fading memories of the Cold War and the CPUSA's pragmatic, grass-roots activism have lessened the stigma around communism - but prejudice endures on the ground.
"I've been called a home-grown terrorist, I've gotten threatening phone calls, I've gotten people showing up at my house who aren't welcome," he says. "Anti-Communism and all that is still very real in terms of the far right wing in our nation and the tea party elements."
"We try to let our work speak for us, and not make it so much about the 'C' word."
Webb says he doesn't get harsh reactions when he tells people he's a Communist. Some younger people - perhaps with only a vague understanding of what the world means - even think it's "cool". But he hints that the party may finally, quietly shed some historical baggage as it builds alliances with other groups on the American left.
Looking ahead to the party's convention in June, he says he wants to create an atmosphere in which "comrades" feel free to raise their concerns, including over the party's name.
"Some feel we ought to consider changing it. Others strongly feel we shouldn't. So we've agreed that we'll allow space for that conversation to take place."