ATLANTA — Karl Sandstrom looked at the room across from where the Democratic Party was about to choose its new leader and shook his head in disbelief.

The scene was chaotic. Pete Buttigieg had just quit the race, and three of the Indiana mayor’s young volunteers were hugging. Two reporters conducting an interview walked briskly past. Hundreds of campaign posters were scattered across the room — dozens of Minnesota Rep. Keith Ellison’s green signs lay on the floor next to a three-foot pile of white-and-blue ads for vice chair candidate Michael Blake.

“You see these signs out here? Never has there been a DNC race like this. We’ve never had this much energy, this many volunteers, this much debate, this much chanting, this much stuff,” said Sandstrom, an attorney for Democratic state parties attending his 10th chair election. “The DNC chair is normally a relatively obscure figure.”

Not anymore. Many Democrats saw this year's election as a chance to heal the wounds of the 2016 primary, as left-wing populists and congressional Democrats joined together behind Ellison, while the party's establishment and veterans of President Obama's administration backed Tom Perez, Obama's former labor secretary. (Perez ultimately beat Ellison on the second ballot by a 235-200 vote margin.)

Ellison’s supporters argued picking him would ensure that Sen. Bernie Sanders’s fans had a home in the Democratic Party. They cast him as a unity choice, arguing he was best positioned to incorporate the outpouring of activism on the streets into the party.

But in Atlanta, many Democrats were convinced they didn’t need Ellison to harness grassroots excitement. It’s not just Sanders’s backers who are energized, they argued. And officials said they are confident that most of the Sanders/Ellison wing will come back into the fold even with Perez as chair — in part to oppose Trump, and in part because Ellison and Sanders are themselves committed to party unity.

Democrats backing Perez: Grassroots energy isn’t just on Sanders left

Ohio Democratic Party Chair David Pepper was one of the few state party chairs who endorsed Perez. (More than 25 publicly endorsed Ellison, and Perez only had a handful of state party endorsements going into Saturday.) Pepper largely dismissed concerns that die-hard Ellison and Sanders voters would refuse to work with the Democratic Party.

“A few will say that, I’m sure, but with what Paul Ryan and Trump are doing, I’m confident we’ll unite,” Pepper said.

The excitement over the DNC race didn’t only come from the Ellison wing, he argued. He noted that while Ellison’s supporters were the loudest, he heard from backers of all three of the leading candidates — Perez, Ellison, and Buttigieg — something he’d never expected to happen in a DNC race.

“The DNC was a very stale organization — every meeting was stale. It was buttoned up. But this is spirited, passionate; you have people running for every level and every position,” Pepper says. “We heard from all comers.”

This was a common refrain among those predicting party unity: that either Perez or Ellison could corral the outpouring of anti-Trump energy, including that from Ellison backers who shared Sanders’s skepticism of the Democratic Party. And once Perez won, he appointed Ellison to be deputy chair.

“Whichever one of them wins, they’re committed to be the voice for the party and come together,” said Stephanie C. Rawlings-Blake, former Baltimore mayor and secretary of the Democratic National Committee, in an interview Friday. “We’re going to find a way to work together.”

Christina Reynolds, the deputy communications director for Hillary Clinton’s presidential campaign and a Perez supporter, added that there was “interest across the board” in grassroots support emerging within the Democratic Party.

“I don’t think it’s just the Bernie wing,” Reynolds said.

Was Ellison necessary as a unity choice?

The powerful idea that Perez could also prove a unity candidate won an unlikely ally: Keith Ellison.

Speaking to his supporters on Friday night, Ellison repeatedly praised Perez. Ellison volunteers said they were told to speak positively about Perez and that party unity was essential for them to believe in, regardless of the outcome.

After praising all of his DNC rivals, Ellison asks supporters for unity: "There is a greater and more important fight out there." — Dave Weigel (@daveweigel) February 25, 2017

As promised, soon after his loss, Ellison rushed to urge his supporters to get behind Perez.

“Here’s what I want to say to [my supporters]: If you care about people ... you have to stay here and support Tom Perez for chair. This is not a small thing; it’s a big thing,” Ellison said. “The fate of our nation is in the balance right now. If they trust me, they need to come on and trust Tom Perez as well.”

Part of this was necessary electioneering — it certainly would have made Ellison’s uphill climb much steeper had he threatened to withhold his faction’s support. But Ellison’s promise to unify the party also allowed Perez’s supporters to reasonably argue that the former labor secretary could also be a unity choice — depriving Ellison of what could have otherwise been one of his strongest arguments.

Some of Ellison’s supporters were free to make the opposite case anyway. Six hours after New York City Mayor Bill de Blasio, an Ellison backer, arrived in Atlanta Friday night, he was still at the hotel bar, trying to persuade undecided voting delegates.

"This is not an optional situation,” de Blasio urged, according to the Washington Post’s David Weigel. “We need Keith Ellison.”

Left-wing groups beyond the Democratic Party sense an opening

Before the vote, Ellison supporters said they worried the grassroots, populist energy would leave the party if Perez won. “The Perez folks don't have anywhere else to go. They’re good Democrats. But that’s not true for a lot for the Ellison folks,” said Cliff Moone, a DNC voting member and Ellison supporter from Hickory, North Carolina.

Two Ellison supporters on Friday admitted they felt the same way. If Ellison lost, said Krupesh Patel, a 30-year-old clutching a green “Keith Ellison for DNC Chair” sign, “it would just look terrible because they're trying to burn the left again.” Scott Brown, 31, nodded in agreement. “There’d be no good reason to say, ‘Hey, the Democratic Party cares about Bernie Sanders’s primary voters,’” Brown says. “This is maybe only our second chance to bring the party together.”

And even Ellison supporters open to the possibility of unity under Perez admitted it would be difficult to achieve. “There's going to be a silent undercurrent that will stay away because they'll feel their voices were not heard,” said Denise D. Adams, a city council member from Winston-Salem, North Carolina.

Calling that faction “silent” might have been too hopeful. When outgoing Chair Donna Brazile announced that Perez had won, a chant broke out among a few dozen Ellison supporters, drowning out the chair at the front of the room: “Party for the people, not big money! Party for the people, not big money!”

A handful of Ellison supporters left the room in anger. Others tried to quiet down their own side, while a Perez supporter yelled across the room for them to be quiet.

Indeed, the country’s two biggest socialist organizations — the Democratic Socialists of America and the Socialist Alternative — immediately moved to use the news of Ellison’s loss for recruitment.

The Democrats do not want to support you. They want to support their elite interests. Workers of the world unite.https://t.co/tFmNlRlurY — DSA (@DemSocialists) February 25, 2017

#DNCChair shows even more that the movement of resistance to Trump's agenda can't be tied to what the Dem establishment is willing to do — SocialistAlternative (@SocialistAlt) February 25, 2017

Alexandria Ellison, the candidate’s 22-year-old niece, said that many of her friends were talking about leaving the Democratic Party if Ellison lost. But Alexandria, like her uncle, said she’d work within the party — and said she thought it was likely many would do the same.

"I think it will be fine,” she said. “Hopefully.”