The impending departure of White House general counsel Don McGahn, confirmed on Wednesday morning by Donald Trump, marks a potential sea change for the president as he turns toward a final battle with special counsel Robert Mueller. Earlier this month, The New York Times broke the news that McGahn had offered unusually extensive cooperation to Mueller’s team, testifying for more than 30 hours about the president’s behavior and state of mind during the firing of F.B.I. Director James Comey, as well as Trump’s efforts to shut down the Russia probe. Speculation immediately turned to how long McGahn would remain in his current role, given his apparent effort to inoculate himself from any criminal liability. “If true, it would raise the question of continued service in the position,” as Bob Bauer, who served in the same position under Barack Obama, told me at the time. “How does a lawyer maintain a professional relationship with a client he suspects of setting him up for criminal investigation, and perhaps prosecution?”

As Trump revealed on Wednesday, the answer is that McGahn will be leaving as soon as possible—“shortly after the confirmation (hopefully) of Judge Brett Kavanaugh to the United States Supreme Court,” which is expected to take place sometime next month. (Axios previously reported that McGahn might remain until after the midterms in November.)

Exact timing aside, McGahn’s exit comes at a critical moment for Trump and the Republican Party. A blue wave could hand Democrats control of the House beginning in 2019, allowing them to initiate congressional investigations, issue subpoenas for information related to the president and his businesses, and begin impeachment proceedings. At the same time, McGahn’s departure is likely to set in motion a series of changes that will fundamentally alter Trump’s relationships with his White House legal team, the special counsel’s office, and his personal attorneys. Last summer, when the president asked McGahn to fire the special counsel, he reportedly threatened to resign. (McGahn’s likely successor, Clinton-impeachment alum Emmet Flood, is expected to be less cooperative with document requests. According to the Times, Flood recently contested a special counsel request to interview Chief of Staff John Kelly, citing the president’s executive privilege.)

The shake-up of the White House general counsel’s office may also precipitate more significant changes to Trump’s relationship with the Justice Department. A key point of tension between Trump and McGahn has been Jeff Sessions’s recusal from the Russia investigation last year, which McGahn reportedly failed to prevent and which Trump views as the “original sin” that set in motion the series of events leading to Mueller’s appointment. In recent weeks, Trump has revived his public attacks on his long-suffering attorney general, and has spoken with his personal lawyers about firing him, according to The Washington Post.

Meanwhile, what was once a largely unified wall of G.O.P. support for Sessions has begun to crack. While Majority Leader Mitch McConnell and other high-ranking lawmakers continue to stand by Sessions, others have seemingly resigned themselves to the inevitability of his firing. “Trump doesn’t like him,” Senator and Trump confidant Lindsey Graham told reporters Tuesday. “This relationship has soured, and I’m not blaming Jeff. It can’t go on like this.” Others have begun signaling that if Trump is to fire Sessions, it should at least wait until after the midterm elections, effectively endorsing an expiration date for the attorney general. “They’d do it before, but they’re worried about the effect it would have on the midterms themselves,” Senator Bob Corker told the Post. “It’s about the investigation, and I think the Mueller investigation ought to go on unimpeded.”