Over at FiveThirtyEight, Harry Enten says First-Debate Losers Aren’t More Likely To Rebound In The Second Debate:
Seven out of nine times, the polls moved by less than about 2 percentage points. Trump is currently behind by 5.6 percentage points in the FiveThirtyEight polls-only popular vote forecast. So Hillary Clinton would still be up by a wider margin than she was heading into the first debate, if Trump got an average second-debate bounce. Still, the polls moved by 5 to 6 points twice, in 1988 and 1992, so such a shift isn’t out of the question.
Unlike first debates, there’s no pattern in which party tends to benefit, the party that holds the White House or the challenging party. Five times the incumbent party gained ground; four times the challenger did. The larger bounces fit this pattern as well. One (1988 for Republican George H.W. Bush) was for the incumbent party, and one (1992 for Democrat Bill Clinton) was for the challenging party.
There’s also no sign that candidates who lose the first debate are therefore more likely to rebound in the second debate.
You can argue about who you think will win tomorrow night’s debate, but you can’t argue that it won’t be interesting. If it’s true Hillary is waiting for the debate to unleash on Trump regarding his hot mic comments about his lewd comments about women including, and I quote, “grab them by the pussy”, then the debate could unravel quickly for Mister Orange Face.