Donald Trump’s campaign is teetering on the brink. He had a horrible first debate, then started sliding in the polls, and then came the release of a 2005 tape in which Trump bragged about being able to sexually assault women. Scores of Republican officials are abandoning him, and Trump probably needs a strong second debate to get back into the race. Given Trump’s recent troubles and lack of debate prep, logic suggests that that will be a challenge. History too suggests that while a second-debate bounce is possible for Trump, it isn’t likely.

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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. Here’s a chart that plots the change in the polls after the first debate compared to the change in the polls after the second debate: