IT’S YOUR TURN TO DRIVE: Hunter S. Thompson, on the lookout for bats.

When Richard Milhous Nixon died in 1994, his old bête noire Hunter S. Thompson summoned the remains of his moribund talent to offer a remembrance. The eulogy hit all the notes expected from the author of Fear and Loathing: On the Campaign Trail ’72—the hell-raising journalist called the departed president a “bastard” and “scum”—but it began on a melancholy note. “It was Richard Nixon who got me into politics, and now that he’s gone, I feel lonely.”

Alex Gibney’s new documentary, Gonzo: The Life and Work of Dr. Hunter S. Thompson, expands on the poignancy of that line, hinting at why Thompson felt so bereaved. It was part of the American genius for polarization that Thompson saw Nixon as his doppelgänger, his mirror. Nixon was his dark shadow. Or maybe it was the other way around.

For the many readers—like myself—who began this summer eagerly devouring Rick Perlstein’s marvelous history book Nixonland: The Rise of a President and the Fracturing of America, these parallels are the most intriguing aspects of Gonzo. The documentary, directed by Gibney (who just won an Oscar for Taxi to the Dark Side), dutifully covers the swath of the mad doctor’s writing, but it is chiefly interested in Thompson the political animal—the man who dogged Nixon through New Hampshire and found his own reflection. Nixon was famously propelled by his resentments toward enemies, real and imagined, who would curtail his lust for power. Thompson’s greed was for libertinism—whiskey, guns and fame—but the resentment was the same. They both saw America as a gated country club, and they nursed their detestation for the men with the keys. And in the end, they both resigned. Nixon, in his elderly fits of sentiment, would tell interviewers he wished he had been a sportswriter. Thompson passed his final days in Colorado typing an insipid column for ESPN.

So it makes perfect sense that when Gonzo recounts Thompson’s last serious journalistic assignment—sent to cover the 1974 Ali-Frazier “Rumble in the Jungle” fight, he swallowed a cabinet of pills and wandered off to float in the hotel pool—Gibney re-creates the scene with washed-out footage of azure water and a man in a Nixon mask. The image is inspired on a number of levels, since this was the moment when a genuinely gifted writer decisively sacrificed his talent on the altar of indulgence, and when he slipped on a mask of celebrity that he would never remove.

The rest of the movie, while amusing and honest, doesn’t often approach that level of perception: It’s content to splash in the shallow end of the pool. Gibney has recruited Johnny Depp to read from Thompson’s books, and in fact we probably hear Depp’s voice more often than Thompson’s, since Gonzo is liberally sprinkled with clips from the Terry Gilliam adaptation of Fear and Loathing in Las Vegas. There are plenty of guest appearances by old cronies, few of whom can stir themselves enough to say an unkind word about the man who squandered his last two decades shooting rifles on his ranch until he finally turned one on himself in 2005. The only regret voiced is one that Gibney repeats several times: Thompson should have stuck around long enough to become a proper foil for the Bush administration.

What Gonzo doesn’t dare say is that Thompson was a fitting adversary for George W. Bush. A writer who had been reduced to a comics-page caricature (Doonesbury’s Uncle Duke) was pitted against a commander-in-chief who borrowed his rhetoric from Justice League panels. What’s more, Thompson had seduced a generation of young pundits into polishing their images as imitation gonzos—embedded with the troops, or shouting bromides about peace, when they might have been investigating a doomed strategy. Hunter S. Thompson—like Richard Nixon—left behind a legacy of pale replicas that helped make America a more partisan, less intelligent place. It’s high time both sides took off the masks.