Late in Monday night's first presidential debate, Donald Trump tried to make the case that Hillary Clinton lacked the basic stamina to do the job which they are both seeking. Here's what he said:

She doesn't have the look. She doesn't have the stamina. I said she doesn't have the stamina. And I don't believe she does have the stamina. To be president of this country, you need tremendous stamina ... You have to be able to negotiate our trade deals. You have to be able to negotiate, that's right, with Japan, with Saudi Arabia. I mean, can you imagine, we're defending Saudi Arabia? And with all of the money they have, we're defending them, and they're not paying? All you have to do is speak to them. Wait. You have so many different things you have to be able to do, and I don't believe that Hillary has the stamina.

It's a line of attack Trump has used before, a way to not-so-subtly raise Clinton's health as an issue -- particularly in the wake of her near-collapse at a Sept. 11 memorial event in New York City earlier this month. It's also a way of suggesting that Clinton isn't telling the whole truth about the state of her health, a whisper campaign that the Democratic nominee emboldened by her secretive handling of a pneumonia diagnosis.

But it just didn't work on Monday night for Trump. Why? See for yourself.

Trump's problem is that Clinton didn't look sick or tired. She didn't cough. She didn't sniffle. (He did. A lot.)

Trump's words questioning whether Clinton was up to the job just didn't match the pictures tens of millions of Americans were seeing on their (split) screens. It was incongruous. That dog didn't hunt.

And it wasn't just any single moment or any single split screen image. As the debate wore on -- it started at 9 p.m. Eastern -- Clinton seemed to warm to the task, looking comfortable, confident and, yes, healthy. Trump, on the other hand, grimaced, leaned on his podium, sighed and seemed to tire -- particularly in the final 20-ish minutes of the event.

Plus, unlike Trump, Clinton was prepared for the stamina attack and had a perfect sound bite at the ready. "Well, as soon as he travels to 112 countries and negotiates a peace deal, a cease-fire, a release of dissidents, an opening of new opportunities in nations around the world, or even spends 11 hours testifying in front of a congressional committee, he can talk to me about stamina," Clinton said to applause from the crowd.

It's this simple: Trump took a stamina swing. And he missed.