Daniel Ellsberg was an ex-Marine, trusted analyst, and Cold Warrior under Secretary of Defense Robert S. McNamara, who, “from the entrails of a bureaucratic war machine”—per a latter-day peacenik cohort—converted to antiwar dove. Leaking 7,000 Xeroxed pages of the Pentagon Papers study to newspapers, Ellsberg gave the world an alternate history of five administrations’ policies in Southeast Asia, and spurred a breached White House into paranoiac espionage ending in presidential resignation. Ellsberg has been resurrected as an “Eternal Left” hero in recent times, publishing a memoir in 2002 and being played by James Spader in a 2003 TV movie. Filmmakers Judith Ehrlich and Rick Goldsmith approach their subject as though burnishing an icon—he withstands the homage well. In old age, Ellsberg is still an articulate interviewee; seen in his years of infamy, he resembles a wiry amalgam of the Cassavetes regulars. The impressive roll call of assembled talking heads includes “Plumber” Egil “Bud” Krogh, who authorized the burgling of Ellsberg’s psychiatrist’s office, and Anthony Russo, Ellsberg’s recently deceased accomplice and RAND Co. co-worker. Most Dangerous Man makes a few distracting embellishments—re-enactments (some shabbily animated), melodramatic cloak-and-dagger scoring—but in the main, it’s a professional job, standing above the crowd of politico documentaries that proliferate like kudzu over arthouse screens.