The important graf:
On or about June 12, 2003, LIBBY was advised by the Vice President of the United States that Wilson's wife worked at the Central Intelligence Agency in the Counterproliferation Division. LIBBY understood that the Vice President had learned this information from the CIA.
Cheney and Libby are not Washington virgins. They know where CPD resides. They know the Directorate of Operations is the clandestine service.
One other thing to remember about Libby: Not only was he chief of staff for Dick Cheney; he was also assistant to the president. Republicans will try to brush off the indictment as "no cancer on the presidency," as David Brooks is trying to do on PBS. But when an assistant to the president is indicted for lying and obstruction of justice, it's a huge deal.