Members of the D.C. bar I spoke with believe that Trump’s safest bet, if he is subpoenaed, is to take the Fifth. But whether the president would be willing to do so is an open question. During the campaign, Trump took a number of shots at individuals who invoked their Fifth Amendment rights in the investigation into Hillary Clinton’s use of a private e-mail server when she served as secretary of state. “The mob takes the Fifth,” candidate Trump said in 2016. “If you’re innocent, why are you taking the Fifth Amendment?”

The political fallout would be immense. “The only real question here is does he decide I can’t politically handle refusing to talk and so do I go in and do it for political reasons and try to be as prepared as possible,” Wisenberg told me. “I happen to think if he does it right, he can invoke the Fifth.” Earlier this year, Robert Bennett, who represented Clinton in the Starr investigation, offered a similar perspective on Trump potentially choosing not to testify. “There’ll be a political impact. Now, how great an impact is hard for me to know. In my own view, in President Trump’s case, people have seemed to have made up their minds about him,” he told me. “His supporters would say, ‘Well, why should he? Everybody knows that the special counsel is out to get him.’ Those who are opposed to Mr. Trump will say, ‘See, he’s hiding something.’”

Trump himself is already fuming over the current state of the investigation, according to the Post. “His instinct is always to be on the offensive,” one source close to the White House told Axios, referring to the leak of Mueller’s prospective interview questions. “This was a wake-up call to the president that will embolden him, in a lot of ways. As he sees this becoming more serious, his instinct is to punch back 10 times harder.” In series of tweets on Wednesday morning, the president’s agita was palpable. “There was no Collusion (it is a Hoax) and there is no Obstruction of Justice (that is a setup & trap),” he wrote. He quoted Fox News contributor Joseph diGenova, a defense attorney who was briefly under consideration to join his legal team, as saying that Mueller’s questions “are an intrusion into the President’s Article 2 powers under the Constitution to fire any Executive Branch Employee” and the “President’s unfettered power to fire anyone.”

What a showdown between Trump and Mueller would mean for the presidency remains to be seen. Critics of the administration worry that a legal challenge would prompt a constitutional crisis, which would almost certainly end with the Supreme Court further chipping away at the president’s executive privilege. “A president who actually cares about the institution of the presidency, I think, would voluntarily cooperate because he would recognize that the fight in court is going to generate precedent that could be potentially adverse to future presidents down the line,” said Katyal. “Here, everything that we’re reading suggests that this is not an indication of privilege for a high-minded reason like protection of the Office of the President but rather to protect Trump and his followers’ own hides. Those are obviously the weakest claims to privilege, and the ones that the courts are most likely to refuse.”

Another powerful Washington defense attorney, who did not wish to be named, offered a more cynical take. “The presidency in the post-Watergate era has been diminished so significantly by Watergate, Iran-Contra, Whitewater and [Bill] Clinton. There’s not many more bad precedents that you can have,” he said, suggesting that the office is already about as weakened as it can get. “Look, we’ve torn down the presidency. I'm not saying it's a good or bad thing, but, I mean, he can be sued civilly. He can be dragged in front of the grand jury. He could have a Secret Service agent testify against him. He has limited ability to claim privilege. I mean, what more can you do to him?”