We're hearing a lot about Donald Trump collapsing in the polls. If you look at the polls Trump doesn't collapsed. On September 18 Trump was down 41.0-40.3 in the RCP average. He’s down 45.8-39.0 now. He’s lost all of 1.3 points from when the race was closest, but Clinton has picked up 4.8 points. While the sex allegations against Trump have hurt him it seems to have drawn Clinton more Johnson, Stein, and undecided voters than Trump voters by a fairly wide margin.
Earlier this year the opinion was floated that Trump was so awful that he'd lose by 20% or even more. It appears that a major party candidate has a floor no matter how bad a candidate he or she is. Even when the news about him is awful, such that he should be abandoned by more people. In 2012 Republicans got 54.7% of the Missouri House congressional vote, but Senate candidate Todd Aiken got only 39.0%. People are willing to be less partisan for the Senate than they are for the President. Trump isn't going to fall 15.7% below the Republican congressional vote. It won't even be close to that.