It’s by now obvious that President Trump is obsessed with the looming Justice Department investigation into Russian meddling in the 2016 election and overlap with his campaign. It’s obvious, too, that part of that obsession centers on disrupting the investigation being conducted by special counsel Robert Mueller. And that disruption depends on Trump having the ability to twist the arms of people in the Justice Department, which appointed Mueller and oversees his work.

Over the past week, Trump had made obvious his annoyance that twisting Attorney General Jeff Sessions’ arm won’t do anything. Sessions recused himself from decision-making related to the Russia investigation after it was revealed that he offered untrue testimony during his Senate confirmation hearings about meetings with the Russian ambassador. So the task fell to Sessions’s number two, deputy attorney general Rod J. Rosenstein. It was Rosenstein who appointed Mueller, to Trump’s annoyance. To oust Mueller, Trump needs someone new as Rosenstein’s boss, meaning that he needs Sessions gone.

Weirdly, Trump hasn’t simply fired Sessions, choosing, instead, to apparently try to humiliate Sessions into quitting. (Firing an attorney general is not without precedent. Harry Truman did it, though under very different circumstances.) As it turns out, there may be a reason for that.