Bernie Sanders arrives for a June 14 news conference in Washington. (Matt McClain/The Washington Post)

It was dinnertime on the first evening of the People’s Summit, and Erin Stewart and Maureen Cruise were arguing about the future of democracy. Stewart, a Seattle-area supporter of Bernie Sanders, was excited about a new online list of “Berniecrats” to support down the ballot. Cruise, who had ditched the Democratic Party for the Green Party five years ago, could not get past the name at the top of that ballot: Hillary Clinton.

“She’s a sociopath,” Cruise said. “When I first saw Bill Clinton speak, I almost fainted. He was so charismatic, he could make fish jump into the boat. But I’ve just learned too much about the Clintons since then.”

The three-day summit, organized by the Sanders-backing National Nurses United, was a happy place to argue about next steps. Sanders supporters, including plenty of elected delegates, came to Chicago’s McCormick Place convention center to share stories and swap causes.

The Democratic Socialists of America hobnobbed with the International Socialist Organization over lawn games. “Fracktivists” from rural Illinois listened to pitches from the Million Hoodies Movement for Justice, with the greatest hits of the Sanders campaign-rally playlist — Simon and Garfunkel’s “America,” Tracy Chapman’s “Revolution” — piping from nearby speakers.

“It’s a lot easier now to talk to people about socialism,” said Tyler Zimmer, one of the ISO’s Chicago organizers, standing by a photo of the Clintons at Donald Trump’s 2005 wedding. “There are people coming to our branches who say they never got involved in politics until Bernie.”

For most of the faithful, the just-concluded Democratic primaries were something to analyze, not move on from. RoseAnn DeMoro, the executive director of NNU, told a packed room of 3,000 activists that Wall Street activists had burrowed like “termites” into the Obama administration.Twelve million voters had not been enough to defeat President Obama’s chosen successor, and some of them intended to lobby superdelegates up until the moment they gave Clinton the nomination.

“We are grieving political losses, dreams tantalizingly tasted but ultimately unrealized,” said the influential left-wing author Naomi Klein at an opening-night panel.

Yet there was little talk of bolting from the Democratic Party to a third party. Jill Stein, the Green Party’s likely presidential nominee, fired off a few Twitter complaints about the organizers keeping her out of the summit. Nina Turner, a Democratic former state senator from Ohio, said in an interview that it would be healthy for a “young, new, burgeoning party” to become an option for progressives. At a Saturday breakout session, where trained facilitators asked fellow activists what to do next, many conversations turned into debates over whether to vote for Clinton or Stein.

That debate ended on the summit’s main stage. Juan Gonzalez, a popular co-host of the left-wing show “Democracy Now,” a TV, radio and Internet news program,asked activists not to repeat the lessons of 1968 when people like him refused to back the Democratic ticket.

“The tactic was wrong,” he said.

Klein told activists about a 2005 workers’ movement in Argentina, where even as they voted, some organizers said that their values were not truly on the ballot.

“It didn’t mean ‘don’t vote,’ ” Klein said. “It meant some people voted and some people didn’t vote. But nobody was under any illusion that what was written on that ballot represented the world that they wanted.”

Sanders, who has drawn down his campaign but not yet conceded, has come out squarely in favor of working inside the Democratic Party. On Thursday night, he told his activists to run for office themselves. On Friday, he announced that 6,700 supporters had committed to do so, allowing them to plot for the future while they debated how hard to work on a 2016 stop-Trump campaign.

“If Trump is even marginally successful it’s going to spawn hundreds of Trump wannabes, and progressives in 2018 will be in this game of Whac-a-Mole,” said Becky Bond, a progressive digital organizer who worked for Sanders’s campaign.

The short-term goal of defeating Trump, she said, would not prevent the Sanders movement from building its own long-term movement. The actress Rosario Dawson won a round of applause when she beseeched Sanders, from the summit’s stage, not to hand his list of millions of small-dollar donors to the Clinton campaign. Bond was more subtle, assuring activists that what Sanders had built would be controlled by his voters, not by any candidate.

“Yes, it was a candidate campaign,” Bond said. “Yes, we focused on issues. But we built a massive voter contact machine that was run not by staff, but that was run by volunteers.”

In hallway conversations and onstage, the issues that separated “Berniecrats” from the mainline Democratic Party were obvious. Some, such as a tax on Wall Street transactions and a $15 minimum wage, seemed achievable inside the party. Some, such as opposition to new military action in the Middle East, seemed impossible if Clinton won the election. Some didn’t even seem to have Sanders’s support, as Chicago activist Tobita Chow admitted when he called for the biggest banks to be nationalized and redirected to social change, instead of just broken up.

“Movements flourish when there are politicians in office who have to be afraid of the movements,” said Frances Fox Piven, an influential left-wing academic and board member of the Democratic Socialists of America. “We don’t want the Democratic Party to become the movement. When movements are roaring ahead, they threaten governability!”

In a few weeks, when Democrats meet in Philadelphia, they will decide how governable they want to be. On Friday night, at the hotel bar closest to the summit, Illinois activists handed out fliers for an all-day Philadelphia conference two days before the Democratic convention. Not far away, the environmentalist and filmmaker Josh Fox played “Ode to Joy” on his banjo and urged people to join him at a rally the next day. On Saturday, members of the “Left Elect” network passed out advertisements for protests every day of the convention, with the slogan “Demonstrate by Day — Strategize by Night!”

Those protests would not be for everyone. Linda Sarsour, a New York activist who had campaigned to win over fellow Muslims for Sanders, had just been elected a delegate to the convention. It would be hard, she admitted, to get behind Clinton.

“Donald Trump just took her down the rabbit hole and made her say ‘radical Islamism,’ even though she promised months ago she would never say that,” she said. “But I’m not ‘Bernie or Bust.’ I come from the number one target class of Donald Trump, so I don’t have that luxury.”