Today's Gallup Daily tracking poll, as I suspected, is showing a return to normalcy. After the convention bounce, McCain's numbers are now falling back to earth (even as his campaign descends into the gutter).
These numbers represent a three-day rolling average, from Wednesday through yesterday. In other words, they are likely rounding the effect of McCain's fall. It's not unreasonable to expect more of the same. And then we'll see where we stand.
(More good news: Nate Silver of 538 points out that the real metric shouldn't be the tracking polls anyway. It's all about the states, and it appears that the bounce, while real, wasn't proportionately spread. In many of the swing states, there was hardly any bounce at all--red states just got redder.)