My bet is Powell, Armitage, or Wilkerson at State. I am sure that once the Pincus and Kristof articles came out, the search was on for the name of this mysterious former US ambassador who had visited Africa on behalf of the CIA.
Has to be one of those three, or Marc Grossman. I have thought all along that the real "war" going on here has been the war between State and CIA. The CIA asked for an investigation of the Plame leak because they thought it came from State and they wanted to nail whoever did it. If Tenet or anyone at CIA had been the leaker, it's nonsensical for CIA to ask for a DOJ investigation. They didn't count on the Kerry campaign turning the whole thing into a political football, forcing the Justice Department to turn the investigation over to a special prosecutor.
Armitage is my bet. I think he turned himself in to Fitz because he found out Woodward was about to name him as the original leaker in a story. This way the heat gets turned back onto Woodward.
The reason this is so great is not only because it will exonerate Libby, but it will blow up Joe Wilson's whole scenario. This was no orchestrated campaign by the political animals in the White House to retaliate against him by outing his wife. It was an attempt by State to make the CIA look bad by revealing that a CIA employee had gotten her incompetent husband sent on an important fact-finding mission that turned out to be so badly handled that they tried to bury it.
There is a big reason why President Bush replaced both Tenet (and Mark Pavitt) and Powell when he did, and replaced them with people who are loyal to him. These two agencies have been at war with each other for years, both had been leaking like sieves, and Bush himself has become the collateral damage.