Last week’s resignation of Michael McKinley from the State Department turns out to have been a big red flag for the White House. The former senior adviser to Secretary of State Mike Pompeo has a lot to say to the House of Representatives, and none of it will make the Trump administration look good. The question will be just how bad it might get:

Michael McKinley, the former senior adviser to Secretary of State Mike Pompeo until his sudden resignation last week, will tell House impeachment investigators Wednesday that career diplomats were mistreated during his tenure and some had their careers derailed for political reasons, according to a person familiar with his testimony.

McKinley will outline how his concerns culminated with the recall of the U.S. ambassador to Ukraine, Marie Yovanovitch, a punitive action he and many other rank-and-file diplomats viewed as wholly unjustified.

“The unwillingness of State Department leadership to defend Yovanovitch or interfere with an obviously partisan effort to intervene in our relationship with Ukraine for the political benefit of the president was too much for him,” said the person, who spoke on the condition of anonymity to be candid.

McKinley left the job last Friday after 37 years of work at the State Department. Pompeo never bothered to thank him for his work, which says something about the relationship between the two within Foggy Bottom. However, McKinley won’t directly go after Pompeo in his opening remarks, according to the Washington Post’s source:

The person familiar with McKinley’s statement said the veteran diplomat will not criticize Pompeo directly, though he will discuss his concern over the politicization of the agency in the Trump administration.

How would that work? If Donald Trump is politicizing the State Department, he’s not doing it by moving into the Secretary of State’s offices. That kind of effort would require at least the cooperation of Pompeo, if not his outright direction. Otherwise, it sounds more like people at State are acting as if rather than being directed — acting as if Trump’s electoral politics are the highest priority, acting as if they are receiving directives. That could very well be true, but it’s not going to stick in an impeachment, where overt actions are needed to effectively establish wrongdoing.

That might just be an opening position in McKinley’s testimony, however. He didn’t resign his 37-year position just to offer the House a 30,000-foot view of the State Department, which he could have done while remaining employed. His resignation is clearly a protest, and that protest reflects those above him in the organization — and there were few if any people besides Pompeo above McKinley at State.

One has to wonder whether McKinley’s resignation and quick turnaround as an impeachment inquiry witness prompted this development today:

Other reports had Volker returning to review his previous testimony. That’s usually something a witness does when they think they have misstated a material fact and need to correct the record before a perjury charge gets leveled. Perhaps it’s just a coincidence, but McKinley’s sudden change of status might mean that Volker’s worried about whether McKinley will contradict him.

Perhaps it has something to do with Volker’s membership in the “Three Amigos” on Ukraine policy, which the Washington Post reported this morning. Volker was the only State Department figure in a triumvirate that managed Ukraine policy, and it was chief of staff Mick Mulvaney rather than Pompeo that was in charge:

Acting White House chief of staff Mick Mulvaney organized a meeting this spring in which officials were determined to take Ukraine policy out of the traditional channels, putting Energy Secretary Rick Perry, U.S. Ambassador to the European Union Gordon Sondland and special U.S. envoy to Ukraine Kurt Volker in charge instead, a top State Department official told lawmakers Tuesday.

George Kent, the deputy assistant secretary of state responsible for Ukraine, told House investigators he was instructed to “lay low,” focus on the five other countries in his portfolio and defer to Volker, Sondland and Perry — who called themselves the “three amigos” — on matters related to Ukraine, Rep. Gerald E. Connolly (D-Va.) told reporters Tuesday. Kent took that as a sign, Connolly added, that having been critical of the plan he was being pushed aside “because what he was saying was not welcome” at high levels of the government.

Mulvaney’s meeting, which Kent told lawmakers took place on May 23, according to Connolly, was just days after the administration recalled Marie Yovanovitch from her post as U.S. ambassador to Ukraine. Yovanovitch spoke to House investigators last week about the campaign against her, which she and other former diplomats have said was organized by President Trump’s personal lawyer Rudolph W. Giuliani.

McKinley would certainly have been in position to see that unfold, as well as what it produced and what its objectives were. That might have made Volker nervous enough to review what he told the House panels earlier.

Still, this leaves some dots unconnected. Presidents have wide latitude in diplomacy and can deputize even “private” citizens for diplomatic missions. That’s why Giuliani’s presence in Ukraine alone isn’t a violation, although given how it’s turned out it wasn’t a great idea either. Two of the “Three Amigos” have been confirmed by the Senate for their current positions, and Mulvaney has an official administration position — more than one, in fact. If Trump trusts them more than some State Department officials to run his Ukraine diplomacy, that’s well within his authority to decide.

Furthermore, presidents have wide latitude to deploy their political agendas through administrative agencies, and State more than most thanks to diplomacy being almost entirely an executive-branch function. Those policies and actions can certainly be scrutinized and criticized, but punishment for unpopular agendas comes most properly from the voters who elected the president. To act otherwise is to transform Congress into a parliament and the executive as its subordinate branch, which would directly conflict with the Constitution.

If, however, the House can establish as a fact that Trump was using congressionally appropriated aid as an explicit quid pro quo for his own electoral purposes, that’s an argument for an abuse of power rising to the level of an impeachment. So far, though, no one’s substantiated that, and at least from the Washington Post’s description of McKinley’s testimony, he’s not going to offer anything like that.

That’s not to say he won’t offer testimony that might be politically damaging to Trump, but it will likely fall more into the “oppo research for 2020” column than legitimately impeachable conduct. That’s still good enough reason for the White House to be very worried about his deposition today, and perhaps for Volker and others to ask for a second look at their earlier testimony.