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