Who cares? Campaigns don't matter outside of PoliGAF and partisan bickering on blogs. The average voter doesn't pay attention to campaigns or polls.
They absolutely do, they just don't know it. The average voter pays attention to the media narrative, and the media narrative is built more than anything around campaigns and polls. Before last night, the worst thing happening to the Romney campaign had nothing to do with how dumb his comments on Libya or whatever were, and everything to do with the media's perception that Romney's campaign was falling apart and their reporting on the Libya matter as such.
By contrast, I think this video might actually move some needles all by itself -- but it's going to get very different coverage from what we'd expect to see if Romney was still hanging tight or even if he was leading. It'd still make the news, because it'll sell papers, but it's going to be called a death knell instead of, say, a painful gaffe that put the race into competition.
So the Senate forecast is out at 538. Democrats 51.2 seats, 70% to control the chamber. Not really news! But good to know.