Barack Obama appears on Letterman tonight and a clip of it was shown on Hardball a few minutes ago where Obama clarifies his metaphor about 'Lipstick on a pig'.
Obama said that if you follow the logic of the metaphor then Palin is the 'lipstick' and McCain is the 'pig'. That's paraphrasing -- watch Letterman tonight to hear for yourself.
But I don't agree completely with Barack on this one. Both McCain and the Pork Princess are pigs and as you can see, they both wear lipstick, too.