Sawant, who is running for re-election for a council seat in District 3, still carries the support of 12 major unions, more than any other candidate in her race, including SEIU Healthcare 1199 NW, SEIU Local 6 and UNITE Here Local 8.

But the broad union backing she once enjoyed has fallen away some. In addition to the reversal of the labor council — the central labor coalition in King County — three chapters of the Teamsters, SEIU 775 and Ironworkers 86 all independently endorsed DeWolf, a member of the Seattle School Board. That's also a change from 2015, when all three groups endorsed Sawant.

DeWolf gained 74 percent of the labor council's support, easily surpassing the two-thirds necessary to win an endorsement.

"It was hers to lose," said Nicole Grant, executive treasurer-secretary of the labor council, following the Wednesday night meeting. "She had it all. She had perfect labor support in 2015. That her endorsement failed and that another candidate with great credentials was endorsed by the labor movement tonight shows that she hasn’t cared for this movement like it needed to be cared for."

In a Thursday morning statement, Sawant pushed back on DeWolf's endorsement. "It's unfortunate that, intentionally or not, a section of labor leaders have made a decision that will effectively further embolden Amazon and the Chamber of Commerce, rather than stand with the interests of working people," she said.

It’s hard to quantify what the endorsements may mean for the race. But even in the era of social media and direct appeals to voters, candidates still court and value support from the traditional institutions that have long held sway in the city’s elections — labor, business, advocacy and neighborhood groups. And with the district-based races forcing candidates to compete for a relatively small electorate, any shift in allegiance has the potential to make a difference.

Two of Sawant's council colleagues, Teresa Mosqueda and Lorena González — both of whom have strong labor backing — have also endorsed DeWolf.

More than just supporting DeWolf, Mosqueda has quietly campaigned against Sawant, whom she once supported.

In a letter sent last week to the labor council’s executive team, urging them to support DeWolf, Mosqueda wrote, “I did not come to the decision to support someone other than Councilmember Sawant easily. Like many of you[,] prior to being on council, I have stood on picket lines and been at rallies that Sawant has supported. I supported her with my own financial contributions and held a fundraiser for her with my family and friends last election.”

But Sawant has made progress difficult by rejecting collaboration, Mosqueda said. An at-large council member, who is not up for re-election this year, Mosqueda noted that she and Sawant “are both union members and agree on at least 90% of policy, yet she continues to speak publicly in opposition to the policies I am working on, then ends up voting yes.”

“Sawant’s responded that she will not work with me to strategize because I work with the other ‘corporate’ council members and she considers me and my colleagues ‘establishment’ — which is an insult to all we’ve done to get more union members and nonestablishment candidates like me in office,” Mosqueda added.

Sawant still retains support from some major entities in the loyal base that swept her into office in a surprise 2013 upset of then-Councilmember Richard Conlin.