Tom Perez has been a member of the Democratic Party’s inner circle for a long time, as an elected official, a candidate, a gubernatorial and presidential appointee and the chair of the Democratic National Committee. He was one of the ablest members of Barack Obama’s cabinet, developing a reputation as a secretary of labor who actually cared about laborers. He has a history of taking reasonably progressive stands on issues, and he has highlighted them as part of his work with the DNC.

Following the disastrous 2016 election, Perez campaigned to become the chair of a party that needed to change. In a contentious race, he was seen as the candidate of an embattled establishment, while Minnesota Congressman Keith Ellison was viewed as the insurgent challenger. After narrowly winning, Perez tried to patch things up by making Ellison the deputy chair of the DNC and touring the country with Vermont Senator Bernie Sanders. More importantly, Perez signaled that he would reverse the reputation of the DNC as a tool of party insiders who were invariably biased in favor of establishment candidates and major donors.

At the heart of this effort was a commitment to remain neutral in primary contests that have now taken on an edge as a “battle for the soul” of the party. For years, grassroots activists have griped that the DNC put its finger on the scale in big-ticket contests—to the advantage of predictable centrists and to the disadvantage of populists who proposed to expand the party’s appeal by exciting the base. The frustration peaked in 2016, during the primary campaign between Hillary Clinton and Sanders, with Sanders backers complaining about everything from the scheduling of debates to the DNC’s approach to resolving disputes over caucuses.

Perez said he was very serious about taking the DNC’s thumb off the primary scale in 2018 and beyond. Acknowledging lingering concerns from 2016—some of which are being addressed by a Unity-Reform Commission process—the chairman said in March: “We’ve got to make sure the process is fair in fact and fair in perception, so everyone feels like they got a fair shake.” The vital thing is that people have confidence in the Democratic Party” and its nominating processes as “open to everyone.”

Restoring and maintaining confidence in the party is a delicate task, especially with lingering mistrust among different factions. As chairman, Perez has used precise language to describe what is necessary to build that confidence. “Scrupulously neutral” was the term Perez employed just last week, when he was asked whether the national party might intervene in the Georgia primary between former legislator Stacey Abrams, a high-profile contender who had attracted significant support from progressive groups that were excited by her base-building campaign to become the country’s first African-American female governor, and former legislator Stacey Evans, who had secured endorsements from former governor Roy Barnes, former senator Max Cleland, and a number of other old-school Georgia Democrats.

On May 18, Perez said the DNC needed to maintain strict neutrality “because we think the voters should decide that.”

That was then. This is now. On May 24, Perez appeared at the New York State Democratic Party convention to deliver an all-in endorsement of Governor Andrew Cuomo and his running mate, Lieutenant Governor Kathy Hochul. “You’ve been delivering results and you’ve been delivering results that have made people’s lives better,” declared the DNC chair. “That’s why Andrew Cuomo and Kathy Hochul are charter members of the accomplishments wing of the Democratic Party, and that’s why I’m proud to endorse them.”

What gives? Both Cuomo and Hochul face spirited primary challenges from progressive Democrats who have captured public attention and endorsements, and who seem to be stirring the imaginations of the younger Democrats and the independents and new voters the party needs. In support of Cuomo’s challenger, Cynthia Nixon, New York Working Families Party director Bill Lipton says: “She is fighting for a New York for all of us, that leaves no one behind. That means fair funding for all our public schools, a criminal justice system that serves all our communities and a campaign finance system that puts working families first, not wealthy donors. We believe Democratic primary voters will choose her as well.” The WFP, which backed Sanders in 2016 and this year is backing many progressive Democrats in primary fights, is also supporting Hochul’s challenger, New York City Councilman Jumaane Williams, whom it hails for helping to “lead the fight to end the abuse of stop-and-frisk, prevent gun violence, and for affordable housing, equity, and social justice.”

So why is the chairman of the Democratic National Committee appearing at a state Democratic convention to endorse a pair of candidates who face hotly contested primaries? Perez says he’s been politically and personally friendly with the Cuomo family for years.

But, as an inner-circle Democrat who has been active in party politics for decades, Perez has (like all party chairs) been politically and personally friendly with a lot of prominent Democrats for a long time. A number of people he knows are running this year. A number of people he knows—including several who played important roles in advancing his political career—might run for the party’s presidential nomination in 2020. Will they too be counted in “the accomplishments wing of the Democratic Party” that somehow merits more generous consideration than the candidates with whom Perez and other inner-circle Democrats are less familiar? Or simply less friendly?

This is a serious question. And a serious issue, which Tom Perez summed up well in March of this year, when he explained during a C-SPAN conversation that the DNC must avoid even the hint of favoritism.

“One thing we’ve learned at the DNC is that when you, in fact or in perception, are trying to put the thumb on the scale in a spirited primary, that can undermine public confidence in us,” said the chairman.

Parties are rarely pure or perfect when it comes to staying clear of primaries, especially when incumbents are challenged.

But Perez articulated a high standard—no thumbs on the scale—which was exactly what was needed.

Then, on Thursday, Perez put his own thumb on the scale in a spirited primary—in fact and in perception. In so doing, the DNC chair undermined confidence in the Democratic Party at a point when it simply cannot afford to be seen as a party that maintains high standards of fairness except when it doesn’t. Tom Perez needs to recognize that this is exactly the wrong impression for the party to be sending about 2018—and 2020.