A nasty mess.
ADDED: Blackfive quotes Sestak's pathetic stonewalling on "Meet the Press" and says:
[T]he fact that Joe Sestak -- even after being called a liar by Robert Gibbs -- has not come forward and made a statement to the authorities about felony corruption he claims to have witnessed says something about Joe Sestak. And what it says is this: Joe Sestak is either a coward, a liar, a political sycophant or -- and this is where I'd put my money -- all three of these things.(Via Fen, in the comments here.)