DNC Chairman Tom Perez speaks to a crowd of supporters at a Democratic rally at the Rail Event Center in April 2017 in Salt Lake City. (George Frey/Getty Images)

On Wednesday, Rep. Keith Ellison (D-Minn.) appeared on the left-wing radio show Democracy Now to explain why “the Democratic Party should stay out of all primaries” and “let the voters decide” their nominees.

Twenty-four hours later, Democratic National Committee chairman Tom Perez walked on stage at New York’s Democratic convention to deliver an endorsement of Gov. Andrew M. Cuomo (D-N.Y.) — who’s facing a primary challenge from actress and activist Cynthia Nixon. Ellison, the DNC’s deputy chairman, was blindsided.

Perez’s speech, coming two weeks before a key DNC committee meets to finalize its 2020 primary rules, has roiled party activists and reopened old wounds. When the Buffalo-born Perez said that Cuomo represented the “accomplishment wing” of the party, he angered Democrats who backed Nixon and worried Democrats who are trying to use the DNC reform process to open up New York’s restrictive voter-registration laws.

“Cuomo can’t help but overreach, and he’s bringing everyone down with him,” said one Democratic strategist working on campaigns in New York.

Perez’s endorsement came after months of infighting between activists and party committees — fights that the DNC, for a while, had managed to avoid. After the Democratic Congressional Campaign Committee published opposition research on Laura Moser, a candidate in Texas’s 7th congressional district, Perez said that his committee would stay neutral.

“What we do at the DNC is we don’t get involved in heavily contested primaries, and the DCCC does,” Perez said in March on CNN.

The DNC chairman stuck to that line for months, telling reporters at a May meeting of the DNC’s rules committee that the party would stay “studiously neutral” in primaries. At the time, the question was about a Georgia contest that a former state lawmaker would win by a landslide. The high-profile Cuomo-Nixon race didn’t come up.

But after Perez walked on stage at Hofstra University, party activists began to ask whether party rules were being tossed aside. The impression that the DNC unfairly advantaged Hillary Clinton’s 2016 campaign had proved hard for the party to shake; it had manifested in everything from conspiracy theories about hacked DNC email, to lawsuits from supporters of Sen. Bernie Sanders (I-Vt.), to low donations despite a national surge of money for Democratic candidates.

For more than a year, a DNC-created “unity reform commission” had met and then peddled its recommendations on how to change the party’s rules. Some of the most bitterly contested reforms had to do with New York and its laws that close primaries to anyone who has not registered as a Democrat within six months of the election. Sanders-backing commission members worried that Cuomo’s clout with the state’s DNC members would lead to those reforms getting shredded.

“If leadership is serious about URC reforms, then why continue to violate DNC bylaws?” asked Nomiki Konst, a member of the unity reform commission. “The Democratic Party is plagued by this problem of not following its own rules. We need to learn the lessons of 2016, and I’m not sure we have.”

The DNC explained Perez’s endorsement in two ways. One, Perez has close ties to New York Lt. Gov. Kathy Hochul, and framed his convention appearance — in part — as solidarity with a friend.

“We knew Kathy when she was fighting in local government,” Perez said. “We were so proud of Kathy when she was serving in Congress. And we’re so proud of Kathy as lieutenant governor.”

Some in the DNC also pointed to a rarely mentioned clause in the “officers agreement,” the rules that govern the conduct of DNC members. “Officers should not attend events or contribute to non-incumbent candidates that have primary challengers (presence could potentially be interpreted as support),” the agreement reads. “However, all officers should feel free to publicly endorse and support incumbent democratic elected officials.”

By that reading, Perez did not break the party’s rules at all. But critics of his endorsement were just as worried about the way he framed it. Hochul, too, is facing a primary challenge from Jumaane Williams, a New York City councilman. And Perez’s praise for Cuomo portrayed him as a pragmatic, progressive governor who had only ever delivered for the Democratic base.

“What I’ve grown to love about Andrew M. Cuomo is that he understands that government isn’t about speechifying,” Perez said. “It’s about making a real difference in peoples’ lives. New Yorkers don’t want rhetoric: They want results.”

But even before Nixon entered the race, liberal groups were working to defeat Democratic state senators who had bolted the party to join the Independent Democratic Conference, a faction that handed power to New York’s Republican minority.

Members of the IDC had only rejoined their party in a deal announced after Nixon entered the race, after Democrats won two special elections that affirmed their majority, and after the state’s budget was complete — with several liberal priorities left out. (Republicans will still control the senate through the end of the year, as another Democrat continues to caucus with them, and to switch leadership mid-session would require a supermajority.)

Ellison, whose DNC role limited some of his political activity, had nonetheless condemned the IDC. In 2017, when he said that breakaway Democrats should be challenged in primaries, IDC members complained that he was further dividing the party. From then on, while critical of the IDC, Ellison stayed away from the primary campaigns themselves.

That led to genuine shock and surprise when Perez endorsed Cuomo. After Ellison’s office put out a short statement restating that he believed in party neutrality, at least one DNC member called him to say he was being divisive. According to a source with knowledge of the call, Ellison was reminded that the party had stood by him in February, when conservative media outlets published a video of him attending an event with Nation of Islam President Louis Farrakhan, resurrecting a controversy that had dogged the Minnesota congressman for years.

Ellison’s office would not comment on the call, and it referred to the statement he had issued after being asked about Perez’s speech in New York: “The Democratic Party should not intervene in the primary process. It is our role to be fair to all contestants and let the voters decide.”