It’s not a dual endorsement — DFA says they may endorse one or the other candidate down the line — but rather, the coalition will serve as a space where left activists and organizations can work together to maximize the number of delegates captured by Sanders and Warren (collectively) and simultaneously continue building the goodwill and solidarity that will be necessary when progressive voters do eventually have to unite behind a single candidate.

“The purpose of this coalition is to make unity possible down the line,” said David Segal, co-founder of the group Demand Progress and a former Rhode Island state representative, “but it’s also to plant a flag in the ground and say to the media and the Democratic establishment: We plan to win. If Warren and Sanders together have a democratic mandate come convention, one of them is going to be president. That’s not negotiable.”

Another priority for the initiative will be to ensure the delegates recruited to represent the candidates are unity-minded. If no candidate enters the nominating convention with a majority of delegates, there will be an opportunity for delegates to shift from one candidate to another. “We want Bernie delegates who are ready to support Warren as their second choice,” Chamberlain said. “And we have to have Warren supporters who are ready to go to Bernie at an open convention.” Once chosen, Chamberlain and Segal envision meet-ups for Sanders and Warren delegates to get to know each other and (hopefully) recognize their common goals.

On the ground in Iowa, DFA and its partners plan to educate voters about strategic caucusing to maximize the two candidates’ delegate haul. Steve Cobble, a progressive activist who was delegate director for Jesse Jackson’s 1988 campaign, explained how this works. “If you’re a Warren supporter and she doesn’t meet the 15 percent threshold to be viable in your caucus site,” Cobble said, “you need to move over to Bernie on your second ballot.” In 2008, Cobble was responsible for convincing candidate Dennis Kucinich to tell his supporters to back Barack Obama on their second ballot — a decision that likely netted the future president a few extra delegates in his tight nominating contest with Hillary Clinton.

For DFA, the unity approach arises out of strategic and organizational necessity. “Together, Warren and Sanders are supported by a supermajority of our members,” Chamberlain said. But those members are, for the moment, split about 50-50 between the two. The Working Families Party, which endorsed Warren in September, faced backlash from Sanders supporters among its membership. The ensuring dispute over its endorsement process — which involved balancing the input of grassroots members and a board of elected chapter leaders — ignited hostilities between Warren and Sanders supporters and damaged the WFP’s credibility with some activists. DFA may be hoping to avoid the same outcome.

WFP communications director Joe Dinkin expressed sympathy for the unity message. “We’re with Warren, but both Warren and Sanders are giants of the progressive movement,” Dinkin said, “and they’re both building the strength of that movement and bringing new people into the fold. Half a dozen candidates are crowding the pro-corporate lane of the Democratic primary. It’s chaos. Progressives are lucky to have two strong, viable, and popular candidates in the race that are fighting to make America work for the many, not just the few.”

When WFP endorsed Warren, they had hoped to inspire other groups to enter the fray. But the strong backlash may have discouraged more early endorsements. For the most part, unions have stayed out of the race as well. But waiting until an obvious frontrunner emerges to invest resources into the race risks allowing a moderate like Biden to consolidate his power uncontested.

That risk is what inspired Archila and CPD to endorse Sanders. “We have a short window to make candidates of the left seem viable,” Archila said, “and to the extent that organizations representing workers and poor people and people of color sit it out, it’s going to hurt us.” Like WFP’s Dinkin, however, she praised both candidates and insisted CPD’s endorsement is not intended to “disparage” Warren. As she sees it, the choice between staying neutral and going nuclear is a false choice — and a destructive one. “I do not abide by the idea that we should destroy our closest ally based on our differences, when we have so many goals in common,” she said.

For the time being, Archila agrees with DFA that having both candidates in the race is good for the movement. “What we need is for both Sanders and Warren to stay on the debate stage for as long as possible so they can continue to define the contours of the conversation and together paint a picture of the country that is in deep contrast with Trump’s exclusionary, racist vision of America,” she said. Unlike journalists, activists, and Twitter warriors, she said, many voters are just tuning in to the primary. When they turn on their TVs, she wants them to see two candidates making the case for Medicare for All, ending deportation, and guaranteed housing. Otherwise, she fears the left’s ideas will be “marginalized” on a stage full of centrists.

And indeed, the only place where real hostility between the Sanders and Warren camps appears to exist is online. “We did a lot of phone calls, meetings, and process to arrive at our endorsement,” Archila said, “and at no point did our people go ‘The other candidate is horrendous!’” Rather, she says, most were very enthusiastic about Warren. “What we heard was, ‘They both speak to us! How exciting!’”

Other progressives see a similar trend. “There are way more people than it might seem who feel good about both candidates,” said DFA communications director Neil Sroka. “That’s the silent majority among progressives.” The unity coalition aims to maintain and cultivate that goodwill. Warren supporters are unlikely to enthusiastically join a Sanders campaign perceived as hostile to their candidate, and vice versa. Without cooperation, progressive leaders fear a circular firing squad and mutual destruction. In an email message to DFA members in December, Chamberlain warned that if supporters of Elizabeth Warren and Bernie Sanders “wage war on each other … [it] will take both of them down.” The point, Chamberlain told me, was this: “Let’s save our firepower for the corporate wing.”

The effort also aims to address an obstacle that is a problem for Sanders in particular. The party power brokers have made no secret that they will do all they can to stop a Sanders nomination, which means that if he comes to the convention under a majority, and doesn’t have Warren delegates to lift him over the top, the party brass will unify around a different candidate. In the spring of 1988, when it briefly looked like Jackson may have been able to arrive at the convention as the delegate leader, party bosses began putting together their own “Stop Jesse” plan that involved nominating Mario Cuomo on the convention floor. In 1976, Jimmy Carter came into a divided convention with roughly 40 percent of the delegates, but was able to claim the nomination. Forty percent might have been enough for Carter, but it wouldn’t have been for Jackson, and it won’t be for Sanders.

“In the Jackson ’88 campaign, we operated on the theory that a delegate who was not explicitly for Jesse would end up supporting his last remaining opponent,” said Cobble. “Bernie could possibly avoid that scenario with the help of other progressive Warren delegates.”

Robinson, of Current Affairs, agreed that it’s important to avoid creating “so much animosity between the two camps that it becomes impossible to unify the left.” However, he sees a problem with being too coy about our differences. “Bernie might not want to criticize Warren directly, but he should certainly draw contrasts,” Robinson said, but he should be more willing to explain why he’s the better candidate. And as for Bernie supporters like him, “I think it’s important to actually criticize things about Warren’s record and politics and her whole method.” Bernie needs to take a more commanding lead over Biden and, Robinson said, “The obvious way to do that is to take those people whose first choice is Warren and second choice is Bernie and flip them.”

David Segal maintains that Sanders is better off continuing to go after Biden voters. “Bernie’s recent tactic of drawing a more explicit contrast with Biden makes sense because Biden’s support is relatively soft — very few of his voters are enthusiastic about him — and in terms of raw numbers, it’s where the greatest number of second-choice Bernie supporters lie.” Meanwhile, Segal explained, hitting Biden serves the cause of unity. “The progressives who make up pluralities of the Sanders and Warren bases are generally unified in their critique of Biden. It’s a signal that they are all on the same team.” In other words, there are fewer votes to be had in attacking Warren, and it risks polarizing the more committed base of her supporters.

“There is no coherent strategic rationale for the campaigns to attack each other,” Segal said.

It’s often assumed in horserace coverage of the primary that Warren and Sanders are competing for the same voters; if one rises in the polls, the other drops. But that’s only partially true. Thirty-one percent of Sanders supporters pick Warren as their second choice, but 29 percent pick Joe Biden and another 9 percent pick Andrew Yang. Similarly, 32 percent of Warren voters pick Sanders as their second choice, but 22 percent pick Biden and 11 percent pick Pete Buttigieg. If Warren dropped out tomorrow, Bernie would gain some voters, but so would his moderate competitors. For instance, with Sanders polling at 20 percent and Warren at 14 in the Real Clear Politics average, Sanders would pick up about 5 percentage points if Warren dropped out, while Biden, who is at 30 percent, would pick up 3 and Buttigieg 2, the rest dispersed. Yes, Bernie gains, but Biden continues his climb toward 50 percent.

Meanwhile, without Warren in the race, as Buttigieg fades, his supporters, who trend older and whiter, would be more likely to drift to Biden than Sanders, meaning that Biden would continue to pull away, unless Sanders could find a way to reverse that dynamic. According to Morning Consult, Biden is the second choice of the most Buttigieg supporters, at 27 percent, followed by Warren at 20 and Sanders at 12 percent. So if both Warren and Sanders stay in the race, the left rises if Buttigieg falls. If only Sanders is in the race when Buttigieg begs off, Sanders would fall significantly relative to Biden.

Robinson argued that such logic only meant that Sanders supporters should hope that Buttigieg stays in as long as possible, not that Warren staying in is good (“It mainly makes me want to donate to Mayor Pete,” Robinson quipped). But if Sanders, Biden, and Buttigieg all arrive at the convention splitting delegates three ways, it’s hard to see that contest tilting toward Sanders and not one of the moderates. Getting to 2,000 delegates — the majority needed — will be difficult for any single candidate, said Larry Cohen, former president of the Communications Workers of America and current chair of Our Revolution, the nonprofit political organization founded by Sanders after his 2016 presidential run.

“It’s a Venn diagram. Not a circle,” Cohen said. Given the power and money behind the establishment wing of the party, Cohen sees unity as the only path to victory for the left. “The math to 2,000, unless Biden totally melts, is tortured. It’s not there. Nobody is getting 2,000.” Having both Sanders and Warren in the race turning out their respective bases and winning delegates may be the likeliest path to a progressive majority at the convention.

For Cohen, who personally supports Sanders and served as the campaign’s liaison to organized labor in 2016, a unity message is not just about singing “kumbaya” and getting along: “It’s not just that we need progressive unity; that’s a nice idea. But this is more than a nice idea. I think there’s a very good chance those delegates will have to stick together. Not just on other issues, like the platform, but to nominate the president.”

How would that work? Well, as Cohen sees it, they can’t wait for a second ballot at the convention. Even if every Sanders delegate moves to Warren or vice versa, the corporate wing will have a chance to consolidate around one candidate, now with the help of an additional 750 nonelected delegates (aka super delegates). In other words, progressives could enter the convention with a majority of elected delegates and leave with Joe Biden as the nominee. “It would be insane for Warren and Sanders supporters to allow that to happen,” said Cohen. Instead, consolidation has to come before just before the convention — the old fashioned way: “One of them drops out, and they make a deal.” Just not yet.