Jefferson Beauregard Sessions III has spent much of his career making enemies. The Alabaman’s strident views have won him plenty of detractors, from civil-rights activists to fellow members of the Senate. But in Donald Trump, Sessions believed he had finally found a champion and fellow traveler. Instead, it seems Sessions has found his most formidable enemy yet.

Trump is now on his second consecutive day of publicly humiliating the attorney general on Twitter, following an interview with The New York Times last week in which he said he wished he’d never appointed Sessions. The attorney general’s decision to recuse himself from investigation into Russian interference in the election infuriated Trump, who has repeatedly tried to end the investigation, including by firing FBI Director James Comey. Instead, Comey’s firing resulted in the appointment of a special counsel to take the case. Here’s Trump’s latest broadside against Sessions:

Not since Andrew Johnson fired Edwin Stanton in 1867, triggering his own impeachment, has a president feuded so openly and bitterly with one of his own cabinet officials. Yet this is even stranger, since Stanton was a Lincoln appointee who was at political odds with Johnson; Sessions, however, is about as simpatico politically with Trump as anyone, and in fact provided much of the policy blueprint for the Trump administration.

The situation is stranger still because, as I wrote yesterday, Trump has the power to fire Sessions whenever he likes. Attorneys general serve at the pleasure of the president. (Johnson was constrained by an act of Congress, since thrown out, that barred the sacking of secretaries.) Trump’s frustration with Sessions about the recusal is not new, and in early June, after news reports revealed his private anger, Sessions reportedly offered to resign. But Trump refused.

Since then, however, the situation has worsened. The legal and political jeopardy facing Trump and his family has increased, including new revelations about campaign contacts with Russia, most notably the June 9, 2016, meeting in which Donald Trump Jr., Jared Kushner, and Paul Manafort sat down with a Russian lawyer, after being promised dirt on the Hillary Clinton campaign. Trump, rightly sensing the danger to his presidency, has become more agitated, and has taken to venting his anger at Sessions publicly. The Associated Press reports that Trump has spoken to aides about the prospect of firing the attorney general.

Yet so far, Trump has preferred to bash him publicly instead. The reasons for this are obscure. Maggie Haberman reports that two sources suggested he’s tormenting Sessions simply because he can, like a cat with a mouse. Despite being famous for the catchphrase “you’re fired,” Trump has shown a notable unwillingness to actually dismiss aides. Meanwhile, he seems at many times to be testing their tolerance for public humiliation.

During the campaign, it took an intervention from his children to push out troubled campaign manager Corey Lewandowski; and rather than fire Manafort, Trump layered him, leaving Manafort to resign on his own. Trump was reluctant to fire National-Security Adviser Michael Flynn, even after learning he lied to Congress. Trump ridiculed Press Secretary Sean Spicer and even excluded the devout Catholic from a much-desired meeting with the pope, but never fired him, and it took Spicer’s own layering by Anthony Scaramucci to drive him to resign. Chief of Staff Reince Priebus has been rumored to be on the bubble more or less since he was hired. Chief strategist Steve Bannon had to suffer a humiliating exile—labeled just “a guy who works for me”—before re-emerging.

Scaramucci, the new White House communications director, who has shown a remarkable willingness to speak about private conversations with the president during his first days on the job, told Hugh Hewitt Tuesday morning that he thinks Trump wants Sessions to resign. Perhaps, like the rumored dismissals of Priebus, Bannon, and Spicer, this one will never come to pass. But then again, Trump never went after any of them as publicly and bitterly as he has Sessions.

Trump’s goal in pushing Sessions out would not simply be personal vengeance. As The Washington Post reports, the thinking seems to be that Trump could appoint a new attorney general—either as a permanent nominee, or as a recess appointee—who could then fire Special Counsel Robert Mueller. Currently, that authority rests with Deputy Attorney General Rod Rosenstein, who is acting attorney general on Russia matters and who appointed Mueller. It’s believed that Rosenstein would refuse to fire Mueller if Trump directed him to do so. Although Rosenstein is himself a Trump appointee, the president purported to know nothing about him and called the Bethesda Republican a Baltimore Democrat during the same Times interview in which he went after Sessions. Perhaps Trump already asked Sessions to fire either Rosenstein or Mueller, and Sessions refused.

Trump has suggested a pattern with law-enforcement officials: First, he tries to cultivate them and get them to kill investigations that could hurt him; then, he fires them, as he did U.S. Attorney Preet Bharara and Comey. Mueller, Sessions, and Rosenstein could easily join that parade.

Sessions was reportedly at the West Wing on Monday. Since a resignation would likely spell the end of the 70-year-old’s political career, he has little incentive to resign beyond avoiding further humiliation. His only public comments on the matter came on Friday at a Justice Department press conference. “I have the honor of serving as attorney general,” he said. “It is something that goes beyond any thought I would have ever had for myself. We love this job. We love this department. I plan to continue to do so as long as that is appropriate.”

While choosing a new attorney general might make it initially easier to fire Mueller, it’s hard to see how it would help Trump in the longer run. The problem with firing Mueller is that it will only enhance the impression—fed, among other things, by Trump’s decision to fire Comey, his repeated insistence that there’s nothing to see, and his son’s rapidly changing account of the June 2016 meeting—that Trump has something to hide. He already stands accused in the court of public opinion of obstructing justice, though he has not been charged with any crimes, and firing Mueller would only make that seem more true.

Trump’s legal authority to fire Mueller, and the permissible and impermissible pathways to do so, are murky and disputed. But trying to do so would almost certainly involve top Justice Department officials resigning or being fired. It seems likely that others at the department might also resign in protest. The precedent is the 1973 Saturday Night Massacre, in which Richard Nixon, seeking to fire Watergate Special Prosecutor Archibald Cox, saw his attorney general and deputy attorney general both resign in protest instead. He eventually got Solicitor General Robert Bork to do the deed, but it was the beginning of the end for Nixon. A judge ruled the firing impermissible, a new prosecutor came in, and within a year Nixon was forced to resign. Firing Mueller, a man with bipartisan respect, would almost certainly set off a political disaster for Trump—though at this point, who could tell the difference between that and the status quo?

Another question is who Trump would appoint to the attorney general’s job. He would likely struggle to find a nominee who was both confirmable by the Senate and willing to do the job.

Confirmation could be especially tough given that Trump’s clear intention in pushing out Sessions is to produce an attorney general who would be willing to fire Mueller. Sessions’s beleaguered state has had the bizarre effect of making an attorney general who is fiercely disliked by Democrats—some accuse him of perjury for not disclosing meetings with Russian officials to the Senate—seem somewhat more praiseworthy, at least for his decision to recuse on Russia. (They would still probably shed few genuine tears for his departure, even if the circumstances worried them.) A Sessions firing or resignation might finally awake the ire of Republican senators, who have made increasingly frantic protestations but have still not undertaken concrete action to constrain Trump. Senator Lindsey Graham of South Carolina issued a statement Tuesday in which he called Trump’s tweet suggesting Sessions prosecute “a former political rival … highly inappropriate.” Graham didn’t say what he’d do if Trump followed through, however.

Even if the Senate were willing, who in his or her right mind would take the job? On Monday, Rudy Giuliani, another top Trump surrogate on the campaign trail who was previously rumored for top administration jobs, said he was not under consideration to replace Sessions. Senator Ted Cruz also said he had no interest. Even before now, Trump has had unprecedented difficulty filling jobs in his administration. Many of the most qualified candidates have either been ruled out because of past criticisms of the president, or have ruled themselves out, not wishing to work for a White House that is beset by chaos, dysfunction, and legal troubles.

Trump’s treatment of Sessions can only make the problem worse. The Alabaman was the first member of the Senate to endorse Trump, and he gave the president both much of his platform and a top aide, Stephen Miller. Sessions was a loyal and staunch defender of Trump through thick and thin, even when the campaign seemed to be foundering. He did so at great political risk to himself, knowing that he’d be an outcast among Republicans if his bet on Trump went bust, as Joshua Green reports in his new book, Devil’s Bargain. Until recently, Sessions seemed to have won the bet. Long a Senate backbencher, he was now the attorney general. But in the last two months, his fortunes have changed. He now faces the prospect of being pushed out of that plum gig just months in the job, having surrendered a safe Senate seat that he could have held as long as he was alive and wished to do so. If that can happen even to longstanding Trump loyalist Jeff Sessions, why would anyone else want the job?