The latest and most glaring sign of President Donald Trump’s growing isolation in the West Wing is his rift with Jeff Sessions, who prior to taking the helm at the Justice Department served as a critical bridge between Trump and Congress as one of the earliest, most vocal supporters of his presidential campaign. Sessions reportedly offered to resign as U.S. attorney general late last month because of the deteriorating relationship.

Trump’s slow-burning fury apparently stems from Sessions’ voluntary recusal from the sprawling federal investigation into Russian interference in the U.S. election, as well as any matters concerning the Trump campaign, according to a bevy of fresh reports from CNN, ABC News, the Washington Post and Politico. The President felt that move was unnecessary, and anonymous sources close to the administration told news outlets that he blames Sessions both for the expansion of the Russia probe and the appointment of special counsel Robert Mueller to oversee it.

Trump also lashed out at Sessions’ Justice Department this week, blaming the agency for the “watered down” second iteration of his executive order temporarily barring immigration from a handful of majority-Muslim countries.

The attorney general’s own frustration with the President, escalated by a series of public and private clashes over the recusal, prompted Sessions to offer his resignation just before Trump left on his first trip abroad as President in late May, according to Politico.

The White House and Sessions’ spokesperson, Sarah Isgur Flores, did not immediately respond Wednesday morning to TPM’s requests for comment.

News of Trump’s anger with Sessions comes as the federal and congressional Russia probes are ramping up, leaving the administration drowning in a wave of negative headlines. The New York Times reported Tuesday night that James Comey, the FBI director who Trump abruptly fired in May, had asked Sessions not to leave him alone with Trump, after the President reportedly asked him to drop the bureau’s investigation into ousted national security adviser Michael Flynn.

Comey is expected to testify about that conversation and memos he kept detailing other conversations he had with Trump about the Russia investigation and its various subplots during a highly-anticipated Thursday hearing before the Senate Intelligence Committee.

The administration has reportedly enlisted a number of Trump allies to make the media rounds to push back on Comey’s testimony, and Trump himself plans to live-tweet the event, according to a Washington Post report.

Four current administration officials, including Director of National Intelligence Dan Coats, Acting FBI Director Andrew McCabe, NSA Director Michael Rogers, and Deputy Attorney General Rod Rosenstein, are also expected to answer questions about the Russia probe and Comey’s firing in a separate Senate Intelligence Committee hearing on Wednesday.

The first few months of Trump’s presidency have been as tumultuous as his campaign, which underwent several staff shakeups and cycled through three campaign managers.

Flynn was the shortest-lived national security adviser in U.S. history, with a tenure of only 24 days. The abrupt firing of Comey, a career federal prosecutor with six years left in his 10-year tenure as the bureau’s director, sent shockwaves through Washington, D.C. The departure of Sessions, who was the first senator to endorse Trump and a top surrogate throughout the 2016, would be similarly astonishing.

As New York Times reporter Adam Goldman noted on Twitter, Sessions’ resignation would allow Trump to appoint a new attorney general who would not have to recuse themselves from the Russia probe. Mueller, the special counsel, would have to answer to that new appointee.

But the Trump administration has had a difficult time finding candidates interested in attaching themselves to a White House that appears to be in free fall. And confirming a new attorney general in the middle of such a fraught political environment would be no easy task.

With Sessions growing increasingly alienated, chief strategist Steve Bannon reportedly zig-zagging in and out of the President’s favor, and Trump beginning to grumble about his son-in-law and senior adviser Jared Kushner, who has come under scrutiny in the various Russia probes, Trump barely has a close ally left in government—and he’s not even half a year into his presidency.