Most are paying more attention to women's beach volleyball and will do so until Labor Day. I think the polls reflected the RNC bounce, the DNC bounce, and are now coming back to where they were before the two conventions. Khizr Khan was one explanation but how many would actually invite him over to their house for dinner?
The talking heads will explain this is a result of the campaign shakeup and the "kinder, gentler" Trump.
However, Trump should have a natural advantage in this election for a number of reasons, not the least of which are that he can walk for more than one block, and stand for 90 minutes without support.