Days before Donald Trump helped draw twenty-four million viewers to Fox for the first Republican Presidential primary debate, Senator Bernie Sanders, of Vermont, took to YouTube for a new-media gambit. Broadcasting from a drab Washington, D.C., apartment, the Brooklyn-bred Democratic candidate delivered a fifteen-minute speech, which was screened for a hundred thousand fans at gatherings around the country. Among the venues registered on the Sanders Web site: “a GMO-free restaurant in the same parking lot as Sapphires Strip Club” (Las Vegas, Nevada), “My Home in the Woods” (Burton, Ohio), and the “Schatsky Family Household” (New York, New York).

“Welcome! Hope everyone got pizza,” eighteen-year-old Ronen Schatsky, a recent Trinity School graduate, said before the broadcast. It was dinnertime at his family’s Upper West Side condo, and Schatsky had procured ten cheese pies for thirty guests—a mix of prep-school comrades and white-haired sixties nostalgists. Those assembled in the living room “to channel our support for Bernie into concrete actions,” per Schatsky’s invite, did not include his parents, the relational psychologist Susan Bodnar and the research strategist David Schatsky. “Ronen just kind of told us he was doing this,” his mother had said earlier, over the phone. The apartment, according to an article called “Teach Your Parents Well,” in Dwell, had been eco-fitted at the behest of Ronen and his sister, when they were eight and five. “I just said they should do a sustainable apartment, and they hired an architect,” said Ronen, who will attend the University of Chicago, after a gap year spent farming in Europe and hiking the Appalachian Trail.

One guest, Liz Friedman, a retired Jewish-community fund-raiser known on style blogs for her enormous colorful jewelry, grumbled about the no-shoes policy. “Very hostile,” she said, still wearing her silver flats.

At seven-thirty, the feed went live. A civil-rights attorney, the only black person visible on either side of the screen, introduced Sanders with talk of police shootings. (Sanders has been dogged by #BlackLivesMatter protesters.) The candidate stuck largely to wealth inequality. “Enough is enough!” he said, calling the Supreme Court’s Citizens United ruling “one of the worst decisions in the history of our country.” In the Schatsky apartment, there was applause for single-payer health care and head-shaking for the campaign worker who urged audiences to volunteer by texting the word “work” to the number “82623.” Schatsky assured his visitors, “We can sign you up without smartphones!”

Fifty blocks south, fifteen leftists sat on plastic stools in a cramped Chelsea home office, and debriefed. They had watched Sanders’s speech on an old iMac. Vered Mallon, a former League of Women Voters official, who was wearing a floral baby-doll dress, remarked, “He was quiet, so he drew you in, not like all the slick ones.” The host was Eric Stenshoel, an intellectual-property lawyer who is also a linguist studying Welsh adjectives. “I’m basically a socialist,” he said, explaining his support for Sanders. “I lived in Sweden for half a year in college.” He shares the two-bedroom apartment with his husband, a tenants-rights activist. Stenshoel said, “We vie for who’s further left.”

The group talked tactics. Grant Siefman, a Whole Foods marketing assistant, suggested petitioning local Democratic delegates: “We’re impossible to ignore right now.” They dispersed at 9 P.M., vowing to begin canvassing. “He’s not Donald Trump,” Mallon said. “He needs us.”

An hour later, at Die Koelner Bierhalle, a hangar of a bar in Park Slope, Charles Carr, the head organizer for the Brooklyn College Democrats, considered Sanders’s appeal. “He’s been chanting these points for decades,” he said. “It’s almost like a nice pair of leather shoes with a reasonable, durable sole. Something that fits very snug, but you know it’s going to stretch over the years and get comfortable and lived-in. Personally, I wear Eccos.” That day, the Dems had formally endorsed Sanders, who spent his freshman year at Brooklyn College, and they’d rallied more than two hundred supporters to the bar. “The last hour has mostly been networking,” Carr said.

Dave Handy, a twenty-seven-year-old progressive strategist, whose firm worked to get Zephyr Teachout on the 2014 New York gubernatorial ballot, said, “I’m Brooklyn for Bernie, and he’s People for Bernie.” He poked a guy beside him—Joe Beuerlein, an actor-bartender. Handy added, “People for Bernie started a Brooklyn for Bernie.”

Another activist interrupted: “People for Bernie and Brooklyn for Bernie are now really New York for Bernie.”

“We’re merging the factions,” Carr said, but he was chastened by Beuerlein.

“ ‘Faction’ is a horrible word. Let’s use ‘group,’ ” he said, over strains of “Stormy Weather.” ♦