I heard George Thoroogood on the radio refer to Mick as "Mick `No Hips' Jagger." Franken's butt is too big to pull off such an impersonation. He's better at stealing Senatorial races.
I've seen this before. The strange thing is that as camp as Mick can be when he wants to, he's never as gay as most Jagger impersonators come across and that's certainly true of Al Franken here. Part of it, I suspect, is body shape. Mick's body shape is so unlike almost any other male that he can pull off those moves and clothing without seeming ridiculous. You just accept it as Mick Jagger. The second someone tries to imitate him, you get Tim Curry in ROCKY HORROR SHOW more than you get Mick Jagger.