Many challengers to the incumbant have gotten a late surge before going down in flames. Jimmah Cahtah comes to mind.
The Jackass Spin Machine is now in full-bore spin mode. By the end of the month, they will be so desperate for good numbers that if they find three people and one of them supports Lurch, they will call it a bounce.
On Fox news a few weeks ago they said, the Republicans get September because of the convention. The challenger gets October. And they get it back again at election time.