So says Slate’s media critic Jack Shafer:

A fossil hunter in search of the origin of the Valerie Plame affair would probably trace it to New York Times columnist Nicholas D. Kristof’s May 6, 2003, piece, “Missing In Action: Truth.” The column cites anonymous sources to report that a former U.S. ambassador had been “dispatched to Niger” after the office of the vice president requested more information about a purported uranium deal between Iraq and Niger. Kristof writes:In February 2002, according to someone present at the meetings, that envoy reported to the C.I.A. and State Department that the information was unequivocally wrong and that the documents had been forged.This passage and a following passage about how the “envoy’s debunking of the forgery was passed around the administration and seemed to be accepted