A correspondent makes the same point as Mark Kleiman here. One way in which Larry Craig's behavior was worse than Vitter's is that Craig "handed the plainclothes sergeant who arrested him a business card that identified him as a U.S. Senator and said, 'What do you think about that?'"
You have here a pretty clear-cut case of Craig trying to use his official position to intimidate the officer and get special treatment. That's true, and it's certainly inappropriate. On the other hand, I do regard this as somewhat mitigated by the fact that I continue to regard Craig's arrest as fundamentally unjustified. The problem, as Josh Marshall points out, is that there was no way Craig could beat the rap without publicly admitting to being gay, which would have been politically (and perhaps personally) untenable. So first he tried to weasel out of the charge, and then he figured maybe he could plead guilty and keep it hushed up. Now he's in an absurd denial pattern.
Fundamentally, though, for me this seems like a sad story about a bad Senator who's going to go down for no particularly good reason only to be replaced by another conservative Republican who's just as bad.