Attorney general nominee William Barr Photo: Chip Somodevilla/Getty Images

President Trump has repeatedly expressed his belief, in public and in private, that the attorney general should act as his personal capo, pressing investigations against his enemies and ignoring violations by his allies. And yet his choice to fill the job (after his first pick infuriated him by refusing to violate clear ethical protocols) is a relatively mainstream choice: William Barr, who held the same position under George H.W. Bush.

A partial answer to the mystery is that Barr has publicly defended Trump on several of his pet issues. He endorsed the firing of James Comey, called for investigation of the Clinton Foundation, impugned the neutrality of Robert Mueller’s investigators, and defended Trump’s practice of demanding investigations of his enemies. Barr has a record as one of the members of the Republican legal Establishment most indulgent of Trump’s conspiratorial mafia ethos.

But a new report in the Wall Street Journal suggests a more complete answer. Earlier this year, Barr wrote a lengthy memo excoriating Mueller’s investigation of Trump for obstruction of justice. Mueller’s investigation was “grossly irresponsible,” had “potentially disastrous implications,” and other choice descriptions spread over 20 pages culled from public reports. This memo was completely unsolicited.

Exactly why he wrote it is a more curious question. According to the Journal’s account, based on people “familiar with the process,” submitted copies of his anti-Mueller memo to Deputy Attorney General Rod Rosenstein and to “the top lawyer representing the White House in the Mueller probe.”

The story implies that Trump was not familiar with the memo when he chose Barr, but does not say so outright. The Journal reports “a second person familiar with the matter said the memo played no role in [Trump’s] decision to choose Mr. Barr.” And it also reports, “After Mr. Trump offered him the job, Mr. Barr briefly told the president that he had written a memo about aspects of the Russia probe that could spur questions during his confirmation hearing, according to a person familiar with the process.”

The story does not say who else the White House counsel shared Barr’s memo with, or whether Trump was ever told of it. It’s entirely possible — indeed, it seems quite likely — Trump was aware of the memo.

The assertion by the Journal source that the memo “played no role” in Trump’s selection of Barr is therefore extremely hard to accept at face value. We know Trump is obsessed with finding an attorney general who will suppress the Mueller investigation. His candidate wrote a memo attacking Mueller, and submitted it to Trump’s lawyer, who may or may not have informed others of the memo’s existence.

The worst-case scenario for Barr is that he opened a covert back channel to the administration and campaigned for the role of being Trump’s Roy Cohn. The best-case scenario is that he merely created the appearance of impropriety. Barr, in this scenario, merely happens to be a fanatical proponent of executive power who expresses his passion for the issue by writing long memos in his spare time. Somehow word of this memo never reached Trump, who then learned of the strange coincidence that Barr had endorsed the very theories that Trump was looking for in the candidate.

Assume for the moment that this latter scenario is true. The most optimistic reading of the Trump administration is that the system has held, and a coterie of professionals have curtailed Trump’s gross autocratic instincts. In this case, then, giving the highest law-enforcement job in the country to an extreme advocate of executive authority, who defends the president’s right to obstruct justice and to demand his own investigations as a matter of abstract ideology would be a grave risk.