At the time, Black was a consultant for e-Smart Technologies, a biometric security technology company that Drizin helped start. Drizin was mired in legal battles over his past convictions. The Republican insider and lobbying powerhouse went to bat on the founder's behalf.

Black's letters, however, were ultimately an exercise in poor judgment. After Drizin had a falling out with e-Smart, Black wrote that same judge a year later asking that his previous advocacy be expunged from the judicial record, an unusual move for such a high-powered figure.

But the episode, mainly because of Black's close proximity to McCain, remains politically relevant. In a separate interview on the matter with Aram Roston, author of "The Man Who Pushed America To War," Black claimed he had not realized the extent of Drizin's controversial past -- an assertion Drizin's lawyer denies.

To critics, Black's actions show the extreme lengths he would go for a business associate -- including calling on the Justice Department to investigate a U.S. attorney for framing Drizin -- only to reverse course as soon as the business relationship turned sour.

Moreover, the episode draws a spotlight back to Black's history of associations with questionable characters and firms, including the private contractor Blackwater USA and even Drizin's old business partner, Ahmad Chalabi.

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