The 1974 political thriller directed by Alan J. Pakula that features a conspiracy to assassinate a presidential candidate is The Parallax View.
Warren Beatty plays Joseph Frady, an investigative reporter who looks into the assassination of Senator Charles Carroll, a presidential aspirant. The official investigation blames a lone gunman, but several witnesses later die, pushing Frady toward the secretive Parallax Corporation.
The film was adapted from Loren Singer’s 1970 novel and also stars Paula Prentiss, Hume Cronyn, and William Daniels. Its story reflects the political anxiety of post-assassination America, while Gordon Willis’s distant, watchful cinematography reinforces the feeling that Frady is constantly being observed.
It is often grouped with Klute and All the President’s Men as Pakula’s “paranoia trilogy.” A common mix-up is The Manchurian Candidate, another assassination-conspiracy film, but that 1962 classic was directed by John Frankenheimer and centers on political brainwashing.