You'd think being in politics, Hillary Clinton would know how to make a proper snide comment but then she says this:
"Vice President Cheney came up to see the Republicans yesterday. You can always tell when the Republicans are getting restless, because the Vice President’s motorcade pulls into the Capitol, and Darth Vader emerges."
Could you make Dick Cheney any cooler with your comparison? Darth Vader. That's awesome. In fact, he's probably one of the few 2nd in command villains that's really really cool, especially in sci-fi. Usually you get crap like that whiny blonde guy in Wrath of Kahn, Starscream, or Sting's character from Dune. Instead, you go and liken Cheney to a complete and total badass. Staying in the realm of Star Wars references, Grand Moff Tarkin is a much less favorable comparison and if you remember your Star Wars movies, he's actually the 2nd in command as far as we know in the original movie (Episode IV).
Maybe at your next stop since Bush has the whole cowboy image going for him, you could liken him to a badass cowboy villain like Liberty Valance, Tim Strong, or maybe Johnny Ringo. That'll really sock it to him.