HMM. THIS A.P. STORY by Deb Riechmann says that Rove and Libby were behind the Plame leak:

McClellan was ordered to say that White House aides Karl Rove and I. Lewis "Scooter" Libby were not involved in leaking Plame's identity. Later, a criminal investigation revealed that they were.

Silly me. I thought it was Richard Armitage.