From that WaPo article:
Wilson's campaign caught the attention of Vice President Cheney's office nearly two months before Plame was unmasked, according to senior administration officials. Cheney's aides pressed the CIA for information about Wilson.
By early June -- one month before Plame was identified in Novak's column -- the State Department had prepared a memo on Wilson's trip that contained a small section about Plame marked "S" for secret. A few days before Novak's column was published, then-Secretary of State Colin L. Powell brought the memo with him on a trip to Africa with Bush and many of his top aides.
