As this Newsweek article explains, Presidential advisor Karl Rove was the source of the leak that Valerie Plame was an undercover CIA agent.

Is this the end for Karl Rove? Slate's Timothy Noah thinks Rove should be fired and has started his Karl Rove Deathwatch. Marshall Wittmann disagrees in this TPMCafe post writing, "for Bush to get rid of Rove, would be like Charlie McCarthy firing Edgar Bergen."