This will be short and sweet. Hillary Clinton wiped the floor with Donald Trump in the first presidential debate Monday night. But it was the way in which she wiped the floor with him that was so interesting.

One of the themes that Trump has hammered on for most of this election cycle has been that Hillary Clinton was weak and lacked the stamina to be president. In contrast, Trump answers every policy question with some variant of saying that the United States needs to be “strong” and “tough.” Whether or not there’s veiled sexism in this line of attack is immaterial at this point. After Clinton’s pneumonia diagnosis a few weeks ago, this attack had the potential to resonate with voters.

What actually happened during the debate, however, was that Trump tried to use every trick in his arsenal to disrupt Clinton and failed. He repeatedly interrupted her but failed to rattle her. Indeed, of the two of them, Trump seemed the frailer one, as he audibly sniffed throughout the entire 95 minutes. Every time Clinton criticized Trump’s business record, Trump couldn’t let it drop. Clinton, on the other hand, was very effective at laughing off most of Trump’s over-the-top hyperbole.

The most interesting thing, however, was that as the debate went along, Clinton got stronger and Trump got weaker. A look at the debate transcript suggests that Trump’s answers got more rambling and more incoherent toward the end of the debate. Clinton remained her steady self.

For example, here’s Trump’s response to the question on U.S. cyberpolicy. It was not his worst answer, but rather a typical one:

We should be better than anybody else, and perhaps we’re not. I don’t think anybody knows it was Russia that broke into the DNC. She’s saying Russia, Russia, Russia, but I don’t — maybe it was. I mean, it could be Russia, but it could also be China. It could also be lots of other people. It also could be somebody sitting on their bed that weighs 400 pounds, okay?
You don’t know who broke in to DNC.
But what did we learn with DNC? We learned that Bernie Sanders was taken advantage of by your people, by Debbie Wasserman Schultz. Look what happened to her. But Bernie Sanders was taken advantage of. That’s what we learned.
Now, whether that was Russia, whether that was China, whether it was another country, we don’t know, because the truth is, under President Obama we’ve lost control of things that we used to have control over.
We came in with the Internet, we came up with the Internet, and I think Secretary Clinton and myself would agree very much, when you look at what ISIS is doing with the Internet, they’re beating us at our own game. ISIS.
So we have to get very, very tough on cyber and cyberwarfare. It is — it is a huge problem. I have a son. He’s 10 years old. He has computers. He is so good with these computers, it’s unbelievable. The security aspect of cyber is very, very tough. And maybe it’s hardly doable.
But I will say, we are not doing the job we should be doing. But that’s true throughout our whole governmental society. We have so many things that we have to do better, Lester, and certainly cyber is one of them.

To the extent that there was an actual response buried in that word salad, it was, “So we have to get very, very tough on cyber and cyberwarfare.” Which is his answer for everything.

Or this, toward the end:

By the end of the debate, after 95 minutes of petulance, Trump claimed that he had a great temperament. The audience spontaneously laughed in response.

Presidential debates are tough, but being the president is tougher. And my main takeaway from tonight’s debate is that Donald Trump doesn’t have the stamina to last four years as America’s commander in chief. Or, as Clinton put it: “I think — I think — I think Donald just criticized me for preparing for this debate. And, yes, I did. And you know what else I prepared for? I prepared to be president. And I think that’s a good thing.”