I've still not seen video reports on the Presidential debate, but I note that sources as diverse as monty, Douthat, and the completely-in-the-tank-for-Trump Powerline blog gave the debate narrowly for Trump. (There are other Trump supporters who, of course, gave it totally to Trump, as you would expect from the alt-right - see Scott Adams - and their dimwitted followers.)
So, I assume, in one sense it would seem that Trump did better than expected - although, obviously, it was about the lowest bar possible that he had to climb over to look more knowledgeable than in the first debate.
But - and here I'll actually cite Adams with semi-approval (even a weirdo can say something useful once in a while): after the first debate, he said that Hillary won it on debating technique, but he thought that on the matter of how it made the audience feel, which he said was more important, he gave it to Trump. (Of course!)
Well, if he's right on the matter of feely perceptions, I can't but get the impression that Trumps strange, intimidating looks and pacing behind Clinton, as well the threat to re-investigate and jail her, were exactly the opposite of what was needed to undo with women the damage caused by the weekend tape. (Adams, of course, being in love with Trump, cannot see this is a result of using his own criteria.)
I therefore would guess that the debate will have next to no positive polling effect for Trump. We'll know in about a week's time.