OK, first off, Mitt used the line with qualifiers, "But you know, when it walks like a duck and it quacks like a duck, typically it's a duck," but the point stuck. Newt is rapidly exiting stage right, now with a visual metaphor on the way out that will sting...
Newt Gingrich as a lobbyist duck.
It is easy to imagine a beak on him, puffed up and quacking. Combined with the devastating actuals regarding Gingrich's lobbying career, I foresee this haunting Newt for some time.
How about adopting the lobbyist duck* as the official mascot of professional lobbyists?
*The image linked is not mine, but is listed as royalty free by one Malin Axelsson (thanks Malin, where ever you are).
I originally heard the quote on Weekend Edition, and got the actual quote from the CNN blog of Rachel Streitfeld.