David Letterman has been losing to Jay Leno for a long time, and losing by a wider margin than ever lately. But last night, a guest appearance by Hillary Clinton helped Dave pull slightly ahead, at least in one night's overnights. It wasn't as big as the last time Hillary appeared with Letterman but last night, it brought in a 4.6/11 rating. Leno only had a 4.4/11, while Ted Koppel had a 3.1/7.