A bored insurance salesman (Timothy Carey) develops a odd philosophy, changes his name from Clarence to "God," and becomes the unwitting tool of Satan (who narrates the film) in the obscure 1962 film The World's Greatest Sinner.
Taken with the energetic performance of an unnamed rock and roll band, he learns guitar, forms a new political party (the Eternal Man party), holds rallies/speeches/concerts, and runs for president. It's all sort of a low-budget Face in the Crowd. Hilliard might die at the end of the movie, but it's hard to tell, it's just that weird.
The film is also notable for having an original score by Frank Zappa, his first.