Advocacy documentaries are a huge risk — such blatantly opinionated content risks alienating viewers, playing to an already established audience, and, in the end, failing to educate anyone. Still, some manage to make a big splash, for better or worse (“An Inconvenient Truth,” “Super Size Me”), but others can truly be sickeningly partisan garbage (anything by Dinesh D’Souza and his manipulative ilk). It’s quite a wide spectrum, but how could it not be? The medium of film is undeniably powerful and people with money have always been eager to exploit it. But the far more mundane reality of advocacy documentary is that so many such films are middling, mediocre exercises that will never find an audience besides those already invested in the cause. Which is likely the fate of “Unfractured,” the new doc that chronicles the life of Sandra Steingraber — a scientist and leader of the anti-fracking movement.

“Unfractured” starts on the steps of New York’s Capitol. Steingraber, with all the conviction and gusto of the generation of enraged environmentalists before her, is laying into fracking, the scientific harms, the exploitation of the masses for the wealth of the few, and general absurdity of a country still somehow having the same debate of science against industry. But Steingraber’s confidence wavers, her voice ringing with a note of sorrow: her husband has suffered a stroke and has been in and out of the hospital. Because his speech has been partially taken, she must speak for them both, she says. It’s a telling moment, and one that sets the tone for “Unfractured.” Directed by Chanda Chevannes, the film has little interest in accumulating facts or proving points. What it’s most interested in doing is digging down into the lives of those who are willing to put their bodies on the line for the causes they care about.

Steingraber’s main objective is to get New York Governor Andrew Cuomo to outlaw fracking in the state. In the face of immense corporate lobbying, though, Steingraber and her compatriots find both dread and flickers of hope. Yet, wherever Steingraber winds up — on a bus to Albany or the Finger Lakes or Romania — she bares the open-wound of her ill husband. The rawness with which she seems to accidentally talk about his condition is moving, and the exhaustion that clearly begins to take its toll as her protests appear to get more and more futile becomes obvious. But “Unfractured” doesn’t seem interested in exploring this tension, the love of family and the willingness to give up everything to protect them, and the reality that, in this case, protecting them means being absent. There is a scene early on where she reflects on the strain, but the film doesn’t seem interested in going back there, despite it being the clear emotional root of the narrative.

That, though, is just one of many of the film’s shortcomings. The most notable of which is the pace. Chevannes’ film gets off to a quick start, following Steingraber from protest to protest to lecture to debate through her life of outspoken advocacy. And soon she’s off to Romania to meet activists fighting off a harmful exploratory operation by Chevron. But then the film stutters. Back in New York, Steingraber and the residents of Seneca Lake take aim at a natural gas storage facility and stage a series of civil disobedience protests. The most fascinating thing about the protests is just how futile and minor they seem. Not only are there just a handful of protesters, but the people on the other side of the fence are their neighbors who clearly have no connection at all to the head honchos down in Texas. And while protests take up much of the middle of the film, they are narratively stalled and tensionless. Even when Steingraber is eventually arrested, the moment is airless and limp.

Everything about all of this — the airlessness, the limpness, the mundanity — says a lot. It speaks to the toil of resistance, the exhaustion, the stagnation, utter lack of progress. But “Unfractured” does it in such an unsatisfying way — there is not even a meager attempt to mine these themes, to understand them, or to even paint this dissatisfying portrait with any sort of flair. What’s most disappointing, though, is how little we actually get to know Steingraber. She’s on screen for almost every minute of the film. However, the moments when she talks to the camera, when she reflects on her experiences and her choices, are easily the most interesting, and they serve only as brief bookends to the film. Which is surprising, considering Chevannes’ last film was also a collaboration with Steingraber, and their rapport should already have been established.

The bigger problem is that “Unfractured” clearly doesn’t know what it wants to be. It is undoubtedly an advocacy film, one openly embracing the anti-fracking cause (it hardly even takes the time to acknowledge any counter arguments — and rightly so), but it also wants to be a portrait of Steingraber, or at least of the daily protester who puts her life toward a greater cause, who is absent from her children to protect their future drinking water, whose husband, victim of a life-altering stroke, must come to visit her in prison. And it doesn’t ever really explore either — not fracking as an issue, or Steingraber as a person — it doesn’t ever feel thoroughly fleshed out. And the film suffers for it. But despite itself, “Unfractured” does manage, nearly incidentally, to capture the indomitable nature of the human spirit, the resilience, the compassion, and, how in the face of all odds, David does sometimes still manage to beat Goliath. [C+]