If that were true, then down-ticket Republicans wouldn't be seeing as much of a sag in their support. And that wouldn't account for the narrow margins in states

If that were true, then down-ticket Republicans wouldn't be seeing as much of a sag in their support. And that wouldn't account for the narrow margins in states where the Republicans usually have stronger positions. And, there's still a fairly high level of undecideds and 3rd-party voters who might switch late (as usually happens)--polls seem to be indicating that these are swinging favorably to Clinton, and not to Trump.