Andrew Sullivan and others have already mentioned this clip by TPMtv, but here is why I think it is important: It does a lot to explain why many people who felt they "knew" John McCain in his earlier DC life have been slow to face and accept what he has become.
The video alternates clips of the "good" McCain, talking about respect and commitment to high-road politics, with ads and other evidence of the way he is running his campaign.
For another time, discussion of whether the "good" McCain was ever an authentic product. I'll just say, many people including me found it appealing at the time. What is undeniable is the contrast between the way he then seemed and the way he now acts. This is obviously an anti-McCain clip, but I think it's instructive even for his supporters. And, in real time before tonight's debate, it shows the range of personas he might choose to project.