Only 20 minutes into the first presidential debate, Donald Trump was rattled. There was still a whole lot of debate to go, of course, but almost as soon as the forum started, Trump appeared anxious, frustrated and, at times, barely capable of containing his anger. In one telling instance, Clinton pointed out, accurately, that Trump has called global warming a hoax created by the Chinese. Trump interrupted her to deny this, but Clinton wouldn't have any of it — she just kept on talking. While only Trump knows what was going on in his head, he looked positively infuriated at being denied the chance to talk.
That was a theme that repeated itself during the debate's opening. When he wasn't talking, Trump looked like he was about to explode. When he did talk, he reverted right back into carnival barker mode — hunching over the podium, shouting into the microphone, interrupting himself mid-sentence, and so on. Trump was not, in any sense of the word, presidential.
Clinton, by contrast, was calm but commanding, collected but confident. She was sure of herself and relaxed, and allowed all of Trump's bombast to slide right off her shoulders. Importantly, she also projected an air of positivity and optimism, a stark contrast to the nervous gloom and doom that Trump embodied.
In one exchange, Clinton accused Trump of not paying any federal income tax for several years in his career, and Trump — rather than deny that this was true — replied, "so that makes me smart." This was a major and completely unforced error; Clinton got Trump to incriminate himself in a big way, and she didn't even have to lay a particularly clever trap to do it. All she did was attack Trump for something he's been attacked on many times before, and Trump immediately tripped over his own ego and into a gaffe.
Nobody can say what the voting public will take away from this forum. But Trump didn't get this debate off to a good start at all.