From Jake Tapper:

The United States Secret Service has dispatched a protective detail to assume the immediate protection of Sen. Joseph Biden, D-Del., a source tells ABC News, indicating in all likelihood that Biden has been officially notified that Sen. Barack Obama, D-Illinois, has selected him to be his running mate.

Let's put it this way: It's either Biden or Clinton. That's about as far as I'm willing to go an hour before midnight. We'll all know in the morning anyway.