Some of the commentators seem to think that Trump's biggest failing was not going after Clinton hard enough on the e-mails, Clinton foundation, Benghazi, etc. I don't agree. The trouble is that when he did go after her, she displayed a poised, even temperament. Even smiled. Clinton isn't easily rattled like Trump is. I have a feeling that Trump will "take the gloves off" more in the next debate but it will either backfire or just not accomplish much.
Trump's biggest problem tonight was his incoherence, particularly down the stretch. It's ironic that he went after Clinton on "stamina." Her stamina is actually amazing. His, not so much.