Who is the mystery person?

From Think Progress

From the CBS Evening News, to air at 6:30PM:

CBS’ JOHN ROBERTS: Lawyers familiar with the case think Wednesday is when special prosecutor Patrick Fitzgerald will make known his decision, and that there will be indictments. Supporters say Rove and the vice president’s chief of staff, Scooter Libby, are in legal jeopardy. But they insisted today the two are secondary players, that it was an unidentified Mr. X who actually gave the name of CIA agent V alerie Plame to reporters. Fitzgerald knows who Mr. X is, they say, and if he isn’t indicted, there’s no way Rove or Libby should be. But charges may not focus on the leak at all. Obstruction of justice or perjury are real possibilities. Did Rove or Libby change statements made under oath? Did they deliberately leave critical facts out of their testimony or did they honestly forget? Some Republicans urged Rove to step down if indicted. Not a happy prospect for president Bush.

Any guesses on the identity of Mr. X?

UPDATE: This bit from the CBS segment is also interesting –

SCHIEFFER: John, I am very interested in Mr. X. Is there any clue or hint as to whether he be - maybe someone who outranks Libby and Rove or would he be a lower-ranking official?

ROBERTS: The best guess is that Mr. X, even though his name is not known and some people are just speculating on who he might be or she might be, is somebody who is actually outside the White House, and in that case would be of a lower rank that both Rove and Libby.

Oh, now I really feel sick. I'm calling out tomorrow right now.