No documentary in history has ever scored a best picture nomination at the Oscars. Not “Hoop Dreams.” Not “The War Room.” Not “Harlan County, U.S.A.” All the classics of the genre failed to make the cut, but the 2009 expansion of the best picture category to up to 10 nominees could work in the favor of “Citizenfour,” Laura Poitras’ superb documentary about National Security Agency whistleblower Edward Snowden.

The film has been hailed by critics for holding up a mirror to our digitally connected and politically fractured present with the intensity of a modern-day “Three Days of the Condor” or “The Conversation.” Its achievement is all the more compelling because unlike those classic thrillers, “Citizenfour” is a real-life drama, with much of the action unfolding in a drab Hong Kong hotel room.

Box office has been brisk, with the film earning nearly $1 million in limited release, an impressive figure for a documentary. The doc is tailor-made to provoke a larger debate on op-ed pages and around dinner tables.

But it’s still not clear whether “Citizenfour” will even earn an invitation to the Oscars despite the reception. As Variety’s Tim Gray noted recently, the 210 filmmakers in the Academy’s documentary branch sometimes steer clear of hot-button political films, denying best documentary nods to Alex Gibney’s “We Steal Secrets: The Story of Wikileaks” and Gabriela Cowperthwaite’s “Blackfish,” for example.

Though all Academy voters are allowed to vote on best picture nominees, the film may prove too provocative. Oscar voters are older and even though Hollywood is a liberal town, Snowden is a divisive figure. Harvey Weinstein, whose Radius-TWC unit is distributing “Citizenfour,” was an outspoken critic of the whistleblower before Poitras’ film changed his mind.

Offering up a slice of cinema vérité that is bolder and more thought-provoking than almost any movie this year, there should certainly be a place for “Citizenfour” in the expanded best picture category. By bringing viewers along as journalists, Glenn Greenwald and Poitras meet with Snowden and prepare to release a series of bombshell reports on the U.S. government’s massive surveillance operations.

When the nominees pool was expanded, there was hope that it would encourage voters to include animated films, foreign movies and documentaries. It worked in the case of animated and foreign language offerings with films like “Amour” and “Up” earning well-deserved nods, but acclaimed documentaries such as “The Act of Killing” and “The Cove” didn’t make the grade.

That’s a shame and it should change. There are worthy contenders this year –“Theory of Everything” presents a portrait of marriage that is both poignant and clear-eyed; “Boyhood” is the perfect coming-of-age story; “Foxcatcher” is an unflinching descent into madness; and “Birdman” with its swooping tracking shots is a technical marvel. Yet not one has emerged as a clear favorite and several other best picture candidates seem more serviceable than galvanizing.

Nothing can match “Citizenfour” for its capacity to inspire passionate and needed debate on the modern surveillance state, the balance between national security and privacy, and the role of the media as a government watchdog. Even if viewers deplore Snowden as a traitor, they come away from Poitras’ film with a deeper understanding of what makes him tick. It’s also masterfully shot by Poitras. Her camera glides over cellphones and lingers besides computer screens as a persistent electronic whirr resounds in the backdrop creating a collage of paranoia.

To be sure, there are flaws. “Citizenfour” elides Snowden’s personal history, Greenwald mugs for the cameras at times and the film sags in its third and final act after its central character flees to Moscow and is barely glimpsed again on screen.

Yet it contains one of the year’s most ambiguous and enduring images: a shot of Snowden and his girlfriend Lindsay Mills as they prepare dinner through the window of their Moscow home. It’s unclear if this is a scene of domestic tranquility or a glimpse of a life of stultifying confinement. Did Snowden flee prison only to find a different kind of captivity?

Among a batch of Oscar contenders that offer tidy conclusions and narrative uplift, that kind of uncertainty may prove too hard to handle.