Of course there's no way to prove this, but I'd be willing to bet that Trump's standing in the polls improving isn't a case of Kamala losing popularity so much as it is Trump gaining popularity - or more precisely, regaining popularity that he's lost. This has happened before - Republicans make noise about abandoning Trump in the wake of a scandal or bad news, he loses support, and eventually the Republicans come crawling back to him. Clearly, Kamala's best chance of winning is to damage Trump close enough to the election that he won't recover his support in time. Less an October surprise than a very early November surprise.