For 40 years one generation after another of left-leaning young moviegoers — the type who are both critics of American foreign policy and connoisseurs of conspiracy theories — have fallen in love with Costa-Gavras’s political murder mystery “Z” (1969). It was a campus and art-house staple in the post-Watergate ’70s and ’80s and the post-Nicaragua ’80s and ’90s. Now Film Forum is bringing it back for a two-week post-Bush engagement beginning Friday.

Building on the documentary style pioneered by Gillo Pontecorvo in “The Battle of Algiers” three years earlier, Costa-Gavras and his cinematographer, Raoul Coutard, produced the template for a thousand political thrillers to come, but the original remains more exciting and more smoothly manipulative than nearly all of its imitators. Yves Montand plays the opposition leader who is murdered, a character based on the actual Greek politician Gregorios Lambrakis; Jean-Louis Trintignant plays the dogged magistrate whose investigation uncovers a vast right-wing conspiracy.