(CNN) The New York Working Families Party, an influential coalition of labor unions and progressive activist groups, voted on Saturday to endorse Cynthia Nixon in her primary challenge to Democratic Gov. Andrew Cuomo.

After hours of discussion, and in defiance of pleas from state committee members pushing to delay the decision, the party formally broke its uneasy alliance with Cuomo, the two-term governor leading Nixon in one early poll by a 3-to-1 margin.

Nixon arrived at the Albany Hilton as debate over the endorsement pinged back and forth in a basement ballroom, only entering to applause after the results of ballot -- which she ultimately carried with 91.5% of the vote -- were confirmed and trumpeted by party leaders.

Taking the podium, Nixon thanked the committee members for their "courage" and called the WFP, which has come under assault this week from inside and out -- with two major unions leaving the fold in protest after it became clear Nixon was all but locked into the endorsement -- the "political home for progressives in New York State, and a source of grassroots muscle for the movement."

"You have stood up," Nixon said as supporters swarmed her and New York City Councilman Jumaane Williams, a lieutenant governor candidate and Nixon's likely running mate. "And you have stood up because you know what I know -- and what the thousands of Americans across this country who are running for office for the first time know. You know and I know and they know that if we want change, if we want a country and a state that works for all of us, if we want that to happen, it's on us."

In so publicly rejecting Cuomo, the small party now finds itself at the center of a wider conflict pitting the state's liberal establishment against a growing progressive movement. To put a fine point on it, Nixon welcomed another endorsement earlier in the day from the New York Progressive Action Network, an organization formed by supporters of Sen. Bernie Sanders' 2016 presidential campaign.

The Cuomo campaign, in a statement released after the WFP vote, touted the governor's liberal record and alluded to his recent role in brokering an end to a power-sharing deal between state Senate Republicans and a breakaway group of Democratic lawmakers.

"After nearly a decade of discord, we have a united Democratic Party, and the governor is 100 percent focused on maintaining that unity to fight Trump in Washington, take back the House and win the state Senate," Abbey Fashouer, a Cuomo campaign spokeswoman, said in a statement. "The schism between the progressive unions who founded the WFP and some of its member organizations is unfortunate, but in that divide the governor stands with the unions who have left the WFP and no longer feel it represents the interests of middle- and working-class New Yorkers."

Endorsement follows days of drama

The WFP vote was, as one attendee muttered on her way into the downtown Albany hotel earlier in the day, "kind of a foregone conclusion" after Cuomo on Friday evening announced he would no longer seek the party's backing. His decision to cede the fight, a move critics dismissed as a transparent attempt to save face, followed a dramatic 24-hour unraveling within the WFP, as union backers fled under what party leaders described as pressure from Cuomo.

"In a meeting earlier this week, the governor was threatening people," WFP State Director Bill Lipton said on Friday. "Several times, he said 'if unions or anyone give money to any of these groups, they can lose my number.' Our friends in labor are in a tight spot, and we respect their decision."

Lipton kept up the conciliatory tone on Saturday, casting the union defectors not as turncoats, but victims of a pressure campaign by Cuomo and his allies.

The Cuomo campaign denied on Friday that the governor threatened anyone -- a message echoed by Héctor Figueroa, president of the Service Employees International Union Local 32BJ -- and cited the union departures when it announced Cuomo would "not be seeking the endorsement of the third party line at (the WFP's) convention next month."

Earlier in the day, two unions crucial to the WFP's organization and financing announced that they would leave the party rather than support Nixon.

"Endorsing Governor Cuomo is the most effective way to put the interest of working families first," said Figueroa and Dennis Trainor, vice president of Communication Workers of America District 1, in a statement. "The latest developments show that the current leadership of the WFP disagrees with that approach, and we have been unable to convince them otherwise. For that reason, we are not attending tomorrow's state committee meeting and will be pulling out of the New York State Working Families Party."

As the rift became clear, and The New York Times published a report detailing a behind-the-scenes pressure campaign, the WFP's Lipton wrote in a fundraising email that unions' absence will "hit us hard." Then he turned his attention to Cuomo.

"I want to be clear about what's happening: rather than go before the members of our State Committee this weekend and make an argument as to why he deserves our endorsement, Governor Cuomo has instead chosen to respond the only way he knows how: retaliating with bullying and threats," Lipton wrote." In doing so, he has put our union sisters and brothers in an almost impossible spot."

After the WFP meeting was adjourned on Saturday, Nixon was asked about the damaging battles of the past few days. Like Lipton, she accused Cuomo of attempting to drive out his political opponents with too heavy a hand -- and worried that it would cripple the organizations that rely in large part on labor's support to fund their work.

"The part of this week that has troubled me the most is the threats that we have heard coming to defund not only the Working Families Party, but the community groups that have failed to endorse the governor," she told reporters. "I don't think the governor's demand for loyalty should go that far. I think this is a democracy and people should endorse the people they want to endorse and not have their livelihoods put in danger."

Cuomo allies pile-on the WFP

While Lipton and activist organizations -- like Make the Road Action, a leading immigrants' rights group that endorsed Nixon on Friday -- were careful to blame the crack-up on Cuomo, at least one labor leader offered a more scathing indictment of the WFP.

Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union, took aim at Lipton on Friday and cast the latest developments as the logical conclusion of a growing, years-long estrangement.

"As a reminder, 90% of the union movement who started the Working Families Party left four years ago -- the only thing that happened today is that the rest of labor followed," Appelbaum said in a Friday statement. "There's no truth to what Bill Lipton is saying -- this is nothing more than a diversionary tactic. Labor is leaving the party we started because Bill Lipton is using it for his own personal agenda."

The pile-on continued into the weekend, as other union leaders lambasted the WFP, which was founded in New York in 1998, for straying from the charter of its founders.

"Mr. Lipton is misguided and delusional if he believes the Working Families Party still represents the voices of labor and working people in New York," said Michael Mulgrew, president of the United Federation of Teachers. "We walked away years ago when it became evident that their focus was on personal political agendas and a few egos. When asked to behave responsibly, they react like children throwing a tantrum in the classroom."

On Saturday, Cuomo's campaign forwarded a statement from Mike McGuire, director of the Mason Tenders District Council, who left the party after 2014.

"The WFP was a good concept," he said, as if mourning its demise. "Unfortunately, it was never allowed to become what it was supposed to be, because the agenda was always driven by the so-called progressives running the staff.

Lipton began Saturday's proceedings by conceding the obvious.

"This has been a rough week for the Working Families Party," he said. It was a line he returned to hours later as WFP staffers rushed to draft and email out highlights from the meeting, before adding with some defiance: "What you're seeing, in this and lots of others around the country, is the emergence of a new national political movement that is saying to the Democratic Party, put working families first, not your donors, or get out of the way."