The Bounce Ends?

We may be seeing a natural peaking in McCain's post-convention numbers:

Overall, the landscape has not changed very much since the Republican convention – we’re just collecting different evidence about where the bounce might or might not be in different states. Arguably, however, there are a few signs that McCain is beginning to come off his peaks. Between the four national tracking polls, McCain now leads by an average of just 0.25 points, his smallest margin since the convention.