Joe Biden embarked today on a treacherous mission, one fraught with the potential to knock the Democratic presidential ticket from its seemingly lofty perch -- behind closed doors, he was raising money in California's Bay Area.

True enough, he could hardly imagine a friendly audience at the three events that will fill his day -- a luncheon, an afternoon reception and a dinner, all at private homes. But that's just why danger lurks. With his guard down, might the voluble Biden make the