Sen. Elizabeth Warren is facing pressure to endorse Sen. Bernie Sanders, her ally in the progressive wing of the party, after exiting the 2020 Democratic primary last week.

On Tuesday afternoon, about 30 former Warren staffers formally endorsed Sanders.

But political operatives say Warren's decision not to throw her support behind Sanders is either a sign she believes his bid is doomed or it illustrates the lack of faith she has in his movement.

"All it says is he's about to get the shit kicked out of him," one Democratic strategist told Insider. "If she thought that there was a path, she would endorse him."

Shortly after Warren dropped out of the race last week, she pointedly called out the "organized nastiness" among Sanders' online supporters. She blamed Sanders for not stepping in to stop it.

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Sen. Elizabeth Warren's decision not to endorse either Sen. Bernie Sanders or former Vice President Joe Biden after dropping out of the Democratic primary last week has drawn some attention to Warren's strategy and motivations in the 2020 race.

Warren faced unusual pressure to throw her support behind a candidate after both former Mayor Pete Buttigieg and Sen. Amy Klobuchar dropped out of the race and endorsed Biden shortly before Super Tuesday.

Many of Sanders' supporters — and some of Warren's — have openly lobbied the Massachusetts lawmaker to endorse the more progressive candidate in the race.

Sanders is facing a key Tuesday contest in Michigan, a state he won in 2016, that will help determine his viability going forward, but pollsters are pessimistic about his chances of ultimately overcoming Biden's delegate lead. Political operatives say Warren's failure to endorse Sanders before Michigan is a sign she won't throw her weight behind him and against Biden.

"Tonight and next Tuesday are crucial for the survival of [Sanders'] campaign," Adrienne Elrod, a Democratic operative and spokeswoman for Hillary Clinton's 2016 campaign, told Insider on Tuesday. "So if you're going to [endorse] and it's going to count and it's going to matter, you'd think that you'd do it now."

One progressive Democratic strategist, who requested anonymity in order to speak candidly, said Warren's failure to endorse Sanders is evidence she thinks the democratic socialist's bid is doomed.

"All it says is he's about to get the shit kicked out of him," the strategist told Insider. "If she thought that there was a path, she would endorse him."

But others say Warren's position stems from more than just a calculation of Sanders' win potential.

"If she really wanted to endorse Bernie, she wouldn't care if he has a chance or not," Elrod said. "She would do it because she thinks it's the right thing to do."

Former Vice President Joe Biden and Sen. Elizabeth Warren onstage before the start of the third 2020 Democratic US presidential debate in Houston, Texas, on September 12, 2019. Mike Blake/Reuters

Progressive consolidation?

Some Sanders supporters blame Warren, at least in part, for their candidate's underperformance on Super Tuesday. They argue that if Warren had dropped out of the race and endorsed Sanders before last Tuesday's contests, Sanders could've consolidated crucial progressive support.

"Imagine if the progressives consolidated last night like the moderates consolidated, who would have won?" Rep. Ilhan Omar, a Minnesota progressive who's endorsed Sanders, tweeted last week. "I feel confident a united progressive movement would have allowed for us to #BuildTogether and win MN and other states we narrowly lost."

And some of Warren's supporters, including former staffers, also wish she'd endorsed Sanders.

"I'm really sad that @ewarren didn't endorse Bernie and I don't see the problem in just saying it when the entire point of the campaign was that you never give up the fight," Tisya Mavuram, a former fundraising associate on Warren's 2020 campaign, tweeted Tuesday.

The afternoon of March 10, about 30 former Warren staffers formally endorsed Sanders.

"We know that we need a bold, ambitious policy agenda for working families, marginalized communities, and our planet," they wrote in a letter. "We know that we won't beat Donald Trump by simply talking about a return to business as usual."

Elrod argued that Warren will likely leverage her influence to push the Democratic nominee to champion her policies, rather than simply give her a prominent job in their administration.

"I can just see her not endorsing or holding out an endorsement until she really thinks … her endorsement of the nominee can make the greatest impact for the policies she's supporting," Elrod said. "I don't see her as being someone who's like, 'Whoever says they're going to make me CFPB chair is who I'm going with.''

But Warren's decision not to immediately take sides in the primary isn't necessarily unusual. Ian Russell, a former deputy director of the Democratic Congressional Campaign Committee, pointed out that, historically, candidates and potential running mates haven't made early, showy endorsements.

"It's not really standard operating procedure for everybody to drop out of the race and endorse somebody," Russell told Insider. "There's never been this precedent that everybody suddenly has to rally around somebody."

Warren has expressed frustration that there's pressure on her to weigh in.

"Why would I owe anybody an endorsement?" she told The Boston Globe last week. "Is that a question they asked everybody else who dropped out of this race?"

Elizabeth Warren at a rally in Detroit on Super Tuesday. Scott Olson/Getty Images

'Organized nastiness'

There is also a more personal dimension to Warren's endorsement decision — or lack thereof.

Shortly after she dropped out of the race last week, she pointedly called out the "organized nastiness" among Sanders' online supporters. She blamed Sanders for not stepping in to stop it.

"I think there's a real problem with online bullying and online nastiness. I'm not just talking about who said mean things; I'm talking about some really ugly stuff that went on," she said in an interview with MSNBC. "We are responsible for the people who claim to be our supporters and do really threatening, ugly, dangerous things to others."

Last month, Sanders was forced to condemn online supporters who harassed the female leaders of Nevada's Culinary Union after the union criticized Sanders' Medicare for All plan.

Also last month, a regional field director for Sanders' campaign in Michigan was fired from the campaign after The Daily Beast reported on misogynistic and otherwise offensive tweets he wrote from a private account targeting other candidates and their supporters. The Daily Beast reporter who wrote the story was later doxxed by Sanders supporters.

When Rep. Alexandria Ocasio-Cortez, Sanders' most influential surrogate, called Warren's Saturday Night Live appearance "legendary," some of Sanders' online supporters attacked the congresswoman.

"We're still dying though. From preventable diseases i mean, not laughter," one critic wrote. "Glad you think it's funny now you've made it to a more comfy class strata though."