What did Donald Trump do today?

He challenged Rex Tillerson to an IQ test face-off, and then sent a surrogate out to explain that he was just joking.

The story so far: last Wednesday, the news broke that Secretary of State Rex Tillerson had called Trump a "fucking moron" in a July meeting and had to be talked out of resigning by Vice-President Mike Pence. Predictably, Trump--who until then had been shielded from the news by aides--was enraged, and forced the normally reclusive Tillerson to make a rare public appearance in which he denied that there was tension between himself and Trump. (He did not, however, directly deny the "moron" remark, which was independently confirmed by other news outlets.) 

Trump channeled most of his anger into attacks on the "fake news" media that had told him about Tillerson's remarks in the first place. But he was still bothered enough during an interview with Forbes two days later to snipe at Tillerson's intelligence:

Forbes: There are reports out today over the last couple days about [Tillerson] calling you a moron privately. Has he talked, reached out to you about that? Do you believe that he said that? 

Trump: Well, we may have to, if he did that--which he says he didn't, by the way, he said he didn't. And they announced with the State Department that he didn't. I think it's fake news, but if he did that, I guess we'll have to compare IQ tests. And I can tell you who is going to win.

That interview was published today, prompting reporters to ask press secretary Sarah Huckabee Sanders the obvious question:

Q. How does the President expect his Secretary of State to be effective when he’s questioning his intelligence? 

MS. SANDERS: Again, he wasn’t questioning the Secretary of State’s intelligence. He made –- 

Q. Why does he think he has a higher IQ, effectively, than the Secretary of State? 

MS. SANDERS: He made a joke. Maybe you guys should get a sense of humor and try it sometime. But he simply made a joke.

That would be easier to believe if Trump were not famously obsessed with his own superior IQ (as he sees it), or if his handlers hadn't already used the joke excuse a few too many times already.

Why should anyone care about this?

• It's bad if a president can be provoked into careless behavior when he's upset.

• It's worse if that president is so easily upset in the first place.

• A president whose "jokes" always need to be explained should probably try to stop "joking."

• A person who has an unshakable belief that he is the always the smartest (or most articulate, or most capable, or least racist, or most emotionally stable) person in the room is probably not the most emotionally stable person in the room.