Hatching schemes that are something of a cross between a Graham Greene novel and Mad Magazine’s “Spy vs. Spy,” Mr. Clarridge has sought to discredit Ahmed Wali Karzai, the Kandahar power broker who has long been on the C.I.A. payroll, and planned to set spies on his half brother, the Afghan president, Hamid Karzai, in hopes of collecting beard trimmings or other DNA samples that might prove Mr. Clarridge’s suspicions that the Afghan leader was a heroin addict, associates say.

Mr. Clarridge, 78, who was indicted on charges of lying to Congress in the Iran-contra scandal and later pardoned, is described by those who have worked with him as driven by the conviction that Washington is bloated with bureaucrats and lawyers who impede American troops in fighting adversaries and that leaders are overly reliant on mercurial allies.

His dispatches — an amalgam of fact, rumor, analysis and uncorroborated reports — have been sent to military officials who, until last spring at least, found some credible enough to be used in planning strikes against militants in Afghanistan. They are also fed to conservative commentators, including Oliver L. North, a compatriot from the Iran-contra days and now a Fox News analyst, and Brad Thor, an author of military thrillers and a frequent guest of Glenn Beck…

“Sometimes, unfortunately, things have to be changed in a rather ugly way,” said Mr. Clarridge, his New England accent becoming more pronounced the angrier he became. “We’ll intervene whenever we decide it’s in our national security interests to intervene.”