Tom Wells, Wild Man : The Life and Times of Daniel Ellsberg
As I'm typing this, I'm wondering if there is any connection between Clarke and Anthony Lake, another associate of Gelb's, who was also a Watergate figure and whom Clinton wanted to appoint CIA Director:
Security Risk for CIA: Plumbing the depths of Anthony Lake's dubious past
Commissioned by Defense Secretary Robert McNamara (CFR) in 1967 to assemble official records on U.S. involvement in Vietnam, the Pentagon Papers study team had access to many top-secret documents. Lake, together with Morton Halperin and Leslie Gelb, was one of the Vietnam Task Force leaders on the project, which was under the supervision of Paul Warnke, an Assistant Secretary of Defense. All members of that quartet were, or would become, (and remain today) members of the Council on Foreign Relations (CFR), otherwise known as the "Park Avenue State Department." Gelb and Lake signed off on the release of the Pentagon Papers to Daniel Ellsberg (CFR), who, in turn, leaked them to comrades at the subversive Institute for Policy Studies and, eventually, to the New York Times and the Washington Post. All of these players -- Lake, Halperin, Gelb, Warnke, and Ellsberg -- soon became activists in the IPS network.