Two things are working for Trump and against Clinton right now. One is completely meaningless: the "basket of deplorables," comment, which will have precisely the same effect as Romney's 47% comment and Obama's guns/religion/anti-immigration sentiment comment: nothing. The second is the pneumonia thing, which sucks because pneumonia sucks, but will only matter if it turns out to be worse than a regular bout of pneumonia, feeding the conspiracy theories, based on the priming issue that I addressed yesterday.
What is notable about both points, though, is that they are transitory. Without a bad turn for Clinton's pneumonia, both stories will fade in a week or so. And they aren't abnormal. As I said with respect to the deplorables, such comments are common for candidates, just as getting sick is common. Note the contrast, then, with the Khan incident. That was abnormal, hence the staying power. It indicated an underlying issue: Trump's basic personality, and that is why he is underperforming relative to a generic Republican right now.
Once the transitory issues fade, the underlying tendencies take over...
... unless the health things are real, but as I've said, I discount Clinton conspiracy theories until the evidence is very strong, and pneumonia isn't strong evidence.