As for the polls and McCain lead at the start of the financial meltdown -- yes, he did have a lead, but it was the remaining part of a very typical convention bounce, slightly dampened by the Dem convention that immediately had preceded it. Nate Silver at fivethirtyeight.com had a good model of the historical trends of post-convention poll bounces, and it was pretty simple to combine the DNC and RNC bounce trends, with a diminished factor for the DNC being eclipsed, and the polling was following a very predictable cycle... after the Biden VP pick, there was some backlash for Obama, and his lead had dropped to about 1.5 points. The DNC raised him to around 9, and then the RNC put them slightly ahead.
It wasn't until the financial meltdown (notably, McCain's weird reaction to it) and the first debate immediately thereafter that there was notable movement off that predicted curve. There's no real reason to think McCain had anything but an ephemeral and temporary slight lead at the time.