Just who the hell does Donald Trump think he is?

Silly question — he's the president of the United States of course, an office that comes with a great deal of power and privilege. But one of the privileges it does not come with is a blanket exemption from the procedures and requirements of the legal system. Which is why there's something bizarre in all the talk and negotiation over whether he'll submit to questions from Special Counsel Robert Mueller. Of course he will. He has no choice. And the very fact that he might try not to should make us all outraged.

There are many questions Mueller wants Trump to answer — about his campaign's involvement with Russia, the actions he took that might constitute obstruction of justice, and some of his business dealings. And like anyone, the president has the option to assert his Fifth Amendment rights not to answer any particular question. He can even assert those rights not to answer any questions at all. But what he can't do is say that he doesn't even have to bother showing up to be asked, simply because he's the president.

For months, Trump's legal team has been negotiating with Mueller for something less than a full interrogation. Maybe Trump could answer some written questions, they offered, or maybe you could stick to only topics we approve, or maybe it could be brief. As Rudy Giuliani told The Washington Post, "It'd be, max, two to three hours around a narrow set of questions."

Trump's legal team is desperate to keep him from testifying, because they are familiar with their client. It's not just his propensity for lying, though that certainly doesn't help; more threatening is his inability to follow instructions and general lack of discipline. After all, this is a man who went on national television and said that he fired former FBI Director James Comey in order to quash the Russia investigation, which is about as close to an admission that he obstructed justice as you could imagine.

And that legal team keeps changing on an almost daily basis, always the sign of a smoothly-running operation. First the person leading it, John Dowd, stepped aside. Then they announced they were hiring Joe diGenova and Victoria Toensing, then they didn't. Then they added a different husband and wife team. Then Giuliani came on board. And on Wednesday, The New York Times reported that Ty Cobb is stepping aside and Emmet Flood, who rather unusually for this crew actually has some relevant experience (he helped represent Bill Clinton during his impeachment and later worked in the Bush White House), will be joining the team. And that's all in just the last few weeks.

This rotating cast of characters hasn't always agreed on how confrontational to be with Mueller, but they all know how dangerous it would be for Trump to testify. But the question is unavoidable: If Trump really is innocent, as he claims, why shouldn't he answer questions?

Ordinarily, there are reasons why someone would choose not to testify in their own defense. Perhaps clever prosecutors would force you into a false confession, or you'd say something that makes you look guilty when you aren't. It happens all the time. But this isn't that kind of situation. This is about much more than whether one person can stay out of jail, and it isn't about matters that should be private. It's about the integrity of our entire system, about infiltration by a foreign power, about corruption, about the official and unofficial actions of the person we selected to sit in the highest office in the land. As much as Trump has gotten away with saying "None of your business" to the American people before (we still haven't seen those tax returns), this would show an unprecedented level of contempt for the public's right to know.

And in the end, if negotiations don't produce an amicable arrangement for Trump's testimony, Mueller has, well, a trump card. He can issue a grand jury subpoena to the president, requiring him to appear at the courthouse (and in a grand jury, he wouldn't be allowed to bring his lawyers).

We've been through a very similar negotiation before, in 1998. Bill Clinton resisted sitting for an interview with independent counsel Ken Starr's team, and eventually Starr got fed up and issued a grand jury subpoena. Knowing he had no other alternative, Clinton relented, negotiating for the interview to take place in the White House instead of the courthouse; Starr then withdrew the subpoena.

Because they eventually arrived at that agreement, the courts never had to rule definitively on whether the president could be forced to testify in this kind of investigation, though there are other related cases strongly suggesting he would have to. Most legal experts seem to agree that if Trump made a blanket claim of executive privilege and said he was refusing to testify, he'd lose — but it would require lengthy litigation that would have to work its way all the way to the Supreme Court.

The president, naturally, is a wee bit perturbed at the whole thing:

This is hardly the first time Trump or one of his defenders has suggested that answering Mueller's questions might subject him to a perjury trap. But here's the thing: You can't walk into a perjury trap unless you're willing to commit perjury.

Most people believe that for the president to plead the Fifth would be a political catastrophe, but I'm not so sure. This is Donald Trump we're talking about. His supporters won't care, since Trump has already convinced them that the entire investigation is illegitimate. He'll be defended by Republicans in Congress. As Trump so insightfully said in 2016, "I could stand in the middle of Fifth Avenue and shoot somebody and I wouldn't lose any voters, okay? It's, like, incredible."

That might apply to a refusal to answer questions about Russia. That immovable support from people who will countenance any behavior on Trump's part, no matter how loathsome or corrupt, might be enough to keep him in office. But that doesn't mean we should treat it as anything other than the scandal it is.