100%? No way.
Still concerned about lots of possibilities. Main one is that Obama is off his peak numbers (might not be anything in particular, just happens), just as he does something pretty risky (the half-hour ad buy). If the off-peak numbers can be linked to the ad (as in, not that they're really linked, but if a semi-credible case can be made for it), then I'm worried that this whole arrogant/ presumptuous narrative will gain a toehold PLUS a whole scrappy McCain comeback not-over-yet narrative.
Not saying I think this WILL happen, but it's scenario #1 in terms of how things could still go bad.