IVRY-SUR-SEINE, France — Appropriately enough, it started with a countdown — “Trois, deux, un, zéro!” — as the onlookers on the outskirts of Paris looked into the sky.
The liftoff on a recent Saturday was surprisingly sluggish, as if the machine rose from the earth only reluctantly. But after gathering momentum, the demolition crane grabbed a chunk of the roof and brought down the first red bricks of “Cité Gagarine,” the huge housing project that once symbolized the success of the French Communist Party, and whose demise now conjured something else.
Christine Deliège, who lived there for 32 years, took off her sunglasses and touched the corners of her eyes, insisting it was only the sun. Her husband, Joel, rolled his eyes.
“It’s a new chapter,” she went on. “We shouldn’t be stuck in the past.”
The same has been said of the French Communist Party, the main left-wing party in the country through the 1970s. It once enjoyed the support of more than 20 percent of the electorate and acted as a kingmaker in many elections.
It also once had a stranglehold on dozens of working-class cities surrounding Paris, an area known as the Red Belt, where the architecture had a tinge of socialism, the streets were named “Lénine,” and the party organ, L’Humanité, was delivered to residents’ doors.
Perhaps no community has been more committed to the cause than Ivry-sur-Seine, an eastern suburb of Paris that has been governed by the Communists since 1925. It is part of Val-de-Marne, the last of France’s 101 departments to still be governed by Communists.
Ivry was where the party built an ambitious housing project in 1961 that embodied its ideals for its working-class supporters: a huge 14-story, T-shaped red brick building with 382 modern apartments and subsidized rents.
As a symbol of the party’s seemingly boundless future, the building was named Cité Gagarine, after the Soviet cosmonaut Yuri Gagarin, the first man in space. The building’s renown was cemented after Mr. Gagarin paid a visit in 1963, and residents threw rose petals at him.
“It was so modern when we arrived,” said Yvette Villefumade, 76, who moved into Cité Gagarine in 1969.
Unlike older public housing, the Gagarine apartments had private toilets, small living rooms, bathtubs — though not the prized spacious kitchens that even newer buildings would eventually have.
“We called them ‘American kitchens,’ ’’ said Ms. Villefumade, whose husband, Daniel Hartmann, lived on Lenin Street at the time.
France’s rapid economic growth drew waves of workers into the factories ringing Paris, creating an acute demand for low-cost housing nearby. By responding to working and living conditions, the Communist Party built a stronghold of loyal voters.
“The Cité became a showcase for the French communist experience,” said Emmanuel Bellanger, an expert on urban history.
But the party began losing members in the 1980s because of two developments that France has grappled with for decades.
The first was overall deindustrialization, which closed factories in Ivry-sur-Seine and the rest of the Red Belt.
The second was the retreat of laid-off workers, who moved away from places like Cité Gagarine, and the arrival of immigrants, mostly from former French colonies in Africa, who filled their apartments.
Between 1980 and 2007, France’s industrial work force shrank 36 percent. Around the same period, the immigrant population rose 1.5 million.
The Communist Party seemed paralyzed. Many of its traditional supporters would gravitate to the far right. And its message failed to resonate with the new arrivals.
“Communists clung to their traditional model of mobilization, which was based on white workers,” said David Gouard, a political scientist who has researched the Red Belt.
Mehdy Belabbas, a Green Party member who sits on Ivry-sur-Seine’s City Council, said that as a young man growing up in Cité Gagarine, he was frustrated that communist activists of North African origins like himself were relegated to minor roles.
To Mr. Belabbas, 41, the rise and fall of Cité Gagarine was a mirror of the Communist Party’s.
“Both reached their peak in the 1960s and 1970s,” he said, “and then declined as they fell short of addressing people’s needs.”
Sarah Misslin, 33, the head of Ivry-sur-Seine’s Communist branch, acknowledged that the party had been “late to grasp social changes.”
“There were many missed opportunities,” she said.
Once a shining symbol of the Communist Party, Cité Gagarine came to represent its powerlessness to some of its own residents.
An elevator that broke down would take months to repair. Cité Gagarine’s jobless rate rose to more than double national unemployment; residents’ income was the lowest in Ivry-sur-Seine. The police came often, responding to drug deals in the halls. In the last years, the rat infestations were common.
Some old-timers, like Ms. Villefumade, felt they had lost their home. The new people had different customs, she said, accusing them of throwing food from their windows.
“I’d find couscous on my windowsill,” she said.
For Walid Bousoufi, 29, whose family moved to Cité Gagarine in 2008, the place felt like a dead end. As he and three friends killed time on barren land near the housing project, they said they had felt “crammed” and “abandoned” in Cité Gagarine, or “Gag,” as they called it.
“There’s no future here,” Mr. Bousoufi said.
The city agreed, deciding to demolish Cité Gagarine and eventually replace it with new housing.
“We reached a point of no return,” said Deputy Mayor Romain Marchand, a member of the Communist Party.
As demolition started on Cité Gagarine, the city organized a full day of events. Posters of the Soviet cosmonaut, waving a white gloved hand, adorned poles in the city center.
As the demolition crane tore into Cité Gagarine’s red brick, Romuald Deschamps, 38, gazed up.
“Did they have to start there?” he said. “That was my bedroom.”
His parents had moved into the corner apartment before his birth, he said, and he had spent his entire life there, leaving only a few months ago.
He couldn’t look away, growing silent, then finally saying, “Time caught up with us.”
At the “Tree of Memories,” people decorated the branches with old photographs of Cité Gagarine, mostly black-and-white shots from the 1960s, when the housing project and the rest of the Red Belt swelled with true believers.
But today, in some corners of Cité Gagarine, things were not as they appeared to be. Even a show of support for the Communists proved illusory.
Among those commemorating the end of Cité Gagarine was Gilles Blanc, 36, wearing a red T-shirt of Vietnam’s Communist Party. A die-hard? A ray of hope for the French communists clinging to their last elected positions with their shrinking and aging backers?
“I’m a pure capitalist,” Mr. Blanc said, an entrepreneur developing educational software for foreign markets, including Vietnam.
“Totally!” he answered.