Warren has the support of several prominent liberal figures and groups, including former presidential contender Julian Castro and the Working Families Party. But a series of strategic and policy moves, particularly on Medicare For All, along with her inability to land the most coveted liberal endorsement of the race—Representative Alexandria Ocasio-Cortez—appears to have cost Warren the chance to lock down the progressive wing of the party that Sanders has been courting for years.

But now that she’s running, many progressive groups and activists have instead lined up behind the liberal who ran against Clinton in her place, Senator Bernie Sanders. The flood of support for the 78-year-old democratic socialist in recent weeks boosts his chances in the still-fluid race and suggests he has the upper hand in their clash to become the progressive standard-bearer heading into the Feb. 3 Iowa caucuses.

“Her engagement with us just wasn’t as deep and hasn’t been as long,” said Bree Carlson, the deputy director at People’s Action, a grassroots activist organization with a million members that endorsed Sanders in December. “We have a lot of history with Senator Sanders.”


This month, the two chairs of the House’s progressive caucus, Representatives Pramila Jayapal and Mark Pocan, backed Sanders over Warren, praising his “authenticity” and joining Ocasio-Cortez and two other members of the so-called progressive “squad” Representatives Ilhan Omar and Rashida Tlaib, in his corner. Sanders also scooped up the endorsements from the youth-powered climate change group the Sunrise Movement, and the grassroots activist organizations the Center for Popular Democracy Action and People’s Action, among several others.

The groups now backing Sanders carry serious clout with with the progressive voters both candidates have spent a year trying to consolidate. Losing these endorsements leaves Warren battling the perception she’s lost her mojo with the left at a time when she needs all the momentum she can get -- as well as bereft of the practical organizational muscle they will provide to Sanders. A recent poll shows Sanders leading the field in Iowa, buoyed by support from voters who describe themselves as “very liberal.”


His success with the left wing of the party this time around wasn’t always a foregone conclusion, given many activists’ deep respect for Warren and a feeling among some that Sanders’ time had passed.

But Sanders immediately set about building on the goodwill he earned after his 2016 run. The day before his campaign launch speech in Brooklyn last year, he met with many of the groups’ leaders in person to ask for their support, making clear their backing was a top priority.

Leaders of the groups backing Sanders stressed that their members liked both candidates and were delighted to have two progressives to choose from, unlike in past elections. But Sanders was willing to go farther than Warren on some key issues, or at least adopt rhetoric that made members feel like he was more committed to their causes.

Warren’s more careful approach to policy in some areas compared to Sanders also appeared to put her at a disadvantage. Sanders and his team vowed to temporarily pause all deportations if he becomes president after receiving feedback from activists from the Center for Popular Democracy Action and other groups—a factor that helped him clinch the activist group’s backing. Warren said she was open to considering the move, but has not officially embraced it.


Sanders reminded the group of his own history of activism, saying he was arrested protesting segregated housing as a 21-year-old at the University of Chicago. “The views that I hold did not come to me yesterday,” he told them.

“People came in expecting a grumpy white guy who knew everything and instead they got a candidate who truly listened to their concerns, who was deeply touched by the stories that they shared and was willing to go farther in his position,” said Jennifer Epps Addison, the group’s co-executive director.

While some pundits worry Warren is too liberal to win the general election—given her embrace of Medicare for All and public battles with Wall Street and billionaires—to the smaller group of liberal activists who have spent years trying to push the party to the left, she’s been judged as just not liberal enough.

Zina Precht-Rodriguez, the national political communications manager for Sunrise, said the group was looking for how fiercely and passionately each candidate spoke about the climate crisis, which ended up favoring Sanders.

Among other things, Sunrise’s activists were impressed with Sanders’ suggestion that fossil fuel executives should be held criminally liable for damaging the environment, even though Warren has already produced a plan that accomplishes a similar goal.

“That’s really aggressive language that we didn’t necessarily see from Warren,” Precht-Rodriguez said.


At certain points last year, it seemed like Warren could usurp Sanders on the left. Warren beat him to the punch on several progressive policy proposals, including her wealth tax and her plan to forgive student loans for most debt-holders and her support for abolishing the 60-vote filibuster threshold in the Senate in order to move more liberal legislation. She also captured progressives’ attention last fall when she endorsed two liberal challengers taking on sitting Democrats in the House—a big statement in Washington, where backing challengers can alienate party leaders. (Sanders backed one, but not both, of those challengers.)

“That was a big signal to a lot of people in the progressive movement” said Waleed Shahid, a spokesman for Justice Democrats, a progressive grassroots group that backed Ocasio-Cortez’s Congressional run and is unaligned in the presidential primary.

In September, Warren landed the endorsement of the Working Families Party, the progressive labor-aligned group that was with Sanders in 2016, and was leading early-state polls while closing in on frontrunner former vice president Joe Biden in national ones. It appeared possible that she, and not Sanders, would emerge as the main progressive challenger to Biden.

But then everything changed.

Sanders’ heart attack in early October was closely followed by Ocasio-Cortez’s endorsement, vaulting him back into the limelight. Several progressive leaders, including Epps Addison and Precht-Rodriguez, mentioned the influence of Ocasio-Cortez, who’s become a liberal social media juggernaut, on their memberships’ endorsement decisions.


“AOC is shaping the future of the progressive left in a lot of ways and definitely influences where these groups want to endorse,” said Shahid. “I think her endorsement meant a lot.”

Meanwhile, Biden and former South Bend, Ind., Mayor Pete Buttigieg began hammering Warren over her Medicare for All plan. It forced her to lay out a detailed “transition” plan that aimed to open up Medicare for a couple of years as an option for Americans before moving to a fully public system. Her two-step plan began to spark doubts among some progressives, even though Sanders has never released a detailed plan for how he would implement Medicare for All.

“That was a big turning point,” Epps Addison said.

Warren has still attracted big endorsements from the left, and several major progressive groups have yet to endorse, including MoveOn, which launched a “Run Warren Run” campaign in 2014. Medicare for All advocate Ady Barkan recounted his support for Warren in an emotional video featuring his battle with ALS addressed to his baby daughter in November. One of the architects of the Green New Deal, Rhiana Gunn-Wright, and the fourth member of the “squad,” Representative Ayanna Pressley of Massachusetts, have also endorsed Warren.

On Monday, a coalition of liberal groups that back Warren, including Working Families Party, Black Womxn For, and the Progressive Change Campaign Committee, plan to roll out 3,000 new endorsements for Warren including elected officials, economists and activists as a show of strength for her on the left. But the list is of individuals, not major organizations.

The endorsements are not just symbolic, and matter more than ever given many large labor organizations that traditionally provide muscle to candidates have sat out the primary so far.

The Center for Popular Democracy Action will knock on doors, conduct phone banks and mobilize volunteers especially targeted at voters of color on Sanders’ behalf, through an independent expenditure arm. Sunrise has volunteers on the ground in early states who will now be advocating for Sanders, and is asking young people to sign pledges promising to vote for Sanders. People’s Action also plans to tap into its network of volunteers in early states on behalf of their candidate.

As Sanders has piled up more liberal endorsements, Warren has leaned into a different strategy: pitching herself as a unity candidate who can rally together the left and center of the Democratic party. From the beginning of the race, she distinguished herself from Sanders by pointing out that she believed in reforming capitalism with tougher rules, not abandoning it altogether. Some online lefties berated her for standing and clapping during President Trump’s State of the Union address last year, when he vowed the United States would “never be a socialist country.”

Some Warren backers have suggested that liberal groups are afraid of raising the ire of Sanders’ fiercest online defenders by endorsing Warren, making Sanders a safer choice.

"It takes extra boldness to endorse Warren because of the vitriol from Bernie Twitter aimed at anyone who acknowledges how amazingly inspirational, progressive, and effective Warren is,” said Adam Green, the co-founder of the Progressive Change Campaign Committee.

And others worry that Sanders’ actual record of getting things done, instead of just talking about them, is going unexamined in some quarters of the left. Lucy Flores, a former Nevada state legislator who backed Sanders in ’16 but has endorsed Warren this time around, said Warren’s past work conceiving of and setting up the Consumer Financial Protection Bureau led her to believe she would be able to actually accomplish progressive ideals--unlike Sanders.

“The fact that she’s got this incredible record of success is a stand out for me and I do think that means something for a lot of people,” said Flores. “The mark of true success is being able to actually pass legislation. And unfortunately Bernie doesn’t have that track record.”

Liz Goodwin can be reached at elizabeth.goodwin@globe.com. Follow her on Twitter @lizcgoodwin