"Senator, I served with Jack Kennedy. I knew Jack Kennedy; Jack Kennedy was a friend of mine. Senator, you're no Jack Kennedy."Over the last 20 years, this has become the archetype not only of the classic debate zinger, but of a meme that takes on a life of its own.
Obama has that opportunity with "lipstick on a pig". Whether he intended it or not, it got under the skin of the McCain campaign. It is short, concise, to the point and easy to understand -- something the cerebral Obama has had trouble with in connecting to some voters. And McCain has used the phrase himself when referring to Hillary Clinton, so his complaints over it are not going to stick.
But most importantly, it perfectly summarizes the entire joke of a campaign that McCain has run into four words. It starts with the central theme that he is something new when he isn't, then adds other valuable imagery: the stupidity of the Palin pick and her vapid self-description; all the pork that Palin claims to be for when she isn't; and the mud-slinging that McCain is so fond of.
Say it early, say it often: "lipstick on a pig".