When Philadelphia District Attorney Larry Krasner announced that he was endorsing Sen. Elizabeth Warren for president, some of his supporters who back Sen. Bernie Sanders lashed out:

“Cancel Krasner.” “Legendary sellout."

“If our revolution helped him get elected, wtf is he doing backing Warren?” went the Twitter responses.

Krasner, viewed as one of the nation’s most progressive prosecutors and a liberal darling, was courted by Warren and Sanders. His backing of Warren surprised some because of the overlap between Sanders’ and Krasner’s supporters in Philadelphia, as elsewhere. Reclaim, the group formed by Sanders supporters after he lost in the 2016 Democratic campaign, helped get Krasner elected district attorney in 2017.

The backlash — however concentrated — reveals friction between liberal voting blocs in the Democratic Party and the difficulty of building a coalition in a heated primary race.

On Thursday, Krasner downplayed the discontent as limited to a tiny corner of the internet. He noted similarities between the two senators and his belief that backers of either candidate would support the other in the general.

“Bernie Sanders and Elizabeth Warren are not attacking each other, in debates and on the campaign trail, because they know better,” Krasner said. “They understand that we are in a moment when the country is going to reject Donald Trump in favor of a more progressive vision than Joe Biden can offer, and it would be foolish in the extreme for these two friends and allies … to turn on each other.”

Sanders’ base is fiercely loyal. Supporters give money to him so frequently he tops the charts in donations received. And few of his supporters donate to other candidates. Many felt he wrongfully lost in 2016 and see him as the original and most authentic banner-carrier for the movement. When the Working Families Party endorsed Warren this summer, a handful of Sanders supporters sent hundreds of angry messages to staffers at the organization.

While Reclaim Philly helped Krasner win in the city with a large cohort of progressive younger voters in the Fishtown, Southwest Center City, and West Philadelphia neighborhoods, his victory was also the result of a broader coalition, including support in many of the city’s predominantly African American neighborhoods. Reclaim has yet to endorse a candidate for president. Its political director, Amanda Mcillmurray, said Krasner’s endorsement was surprising but not a shock.

“I think people put a lot of stock in this one politician is going to be able to change things and feeling like their hope is being stolen from them," Mcillmurray said. "It’s important for us to continue to hold Larry accountable, but that doesn’t mean determining who he supports in different races.”

Krasner has been a Sanders guy in the past. He voted for him. He’s been photographed in a Hindsight Is 2020 T-shirt with a picture of Sanders on it. The two did a criminal justice roundtable in May 2018.

But in the end, he said it came down to who he believes can best implement liberal policies.

Some of Sanders supporters said they see Warren as more moderate, despite proposals considered liberal.

“Just the fact that she was a Republican," said Nikki Walter, a Sanders supporter who lives in West Philly. “I mean, she voted for early-stage-dementia Reagan.” (Warren has said in interviews that she did not vote for Ronald Reagan)

But Walter said she’d gladly back Warren if she is the nominee and thinks the frustration is mostly bluster.

“In my experience and my circles, it tends to be that people who are on Twitter and care that much about politics tend to just lose their mind a little bit," she said. "I think that some people are kind of in a rush to Hillary-ize [Warren] and I don’t think she’s that far right.”

Others insisted that when it comes to criminal justice reform, Sanders has the better track record.

“As someone who volunteered for [Krasner’s] campaign, I’m definitely disappointed,” said Jonah Gardner of the Philadelphia chapter of Democratic Socialists of America, which has endorsed Sanders. “If Krasner is opposed to change on the scale Bernie is arguing for, it makes me wonder how committed he still is to this fight.”

Mcillmurray said she personally supports Sanders (she was a delegate for him and a campaign staffer) but Warren is a close second.

“Both are saying things aren’t working, and we need to radically transform what’s happening," she said. "They just have a little bit different ideas of how.”

Krasner stressed that even Sanders has voiced support for a Warren presidency: “I have not forgotten and no one should forget that Bernie Sanders, early in his prior campaign for president, said the only reason he ran was that he couldn’t persuade his friend Elizabeth Warren to run for president. I heard what he said, and I remembered what he said."

This story has been updated to reflect that Sen. Warren has said she did not vote for Ronald Reagan.