A bit out of date, but still amusing:

The GOP Primary Field in Buffy Villains

Some good choices there, although I personally see Huckabee as the Mayor: Presents a friendly, "family values" personna on the outside, twisted and evil on the inside.

There's a lot of debate in the comments about who Giuliani should be. The author picked Angelus, but that doesn't seem like a good fit. Several commenters have mentioned Glory, while others have mentioned Principal Snyder, based on the resemblance. However, I like the choice made in this blog the best:

Illyria.

Constantly obsessing about a moment of glory in his past, to the point where it's become pathetic. Convinced that this past moment of glory still makes him impressive and intimidating and worthy of respect... and prone to getting very agitated when people don't share this opinion. Nowhere near as powerful as he used to be, but still a threat. Not completely incapable of human feeling, but ultimately craven and self-centered.

Technically, she's an Angel villain, but so what?

Incidentally, although they aren't candidates, I'd say Cheney is "The First," Rove would be the senior partners from Wolfram & Hart, and I think this villain would be the perfect match for Ann Coulter