“I’m not a bad guy,” Steve Butler insists, and one of the reasons “Promised Land” works is that he’s right. Played by Matt Damon (who wrote the screenplay with John Krasinski), Steve, a corporate predator who is also a true believer in his company’s cause, is both the apparent villain and a magnet for the audience’s sympathy.

That cause is the contentious drilling technique for natural gas known as fracking, which has caused an economic boom — as well as considerable environmental worry — in places that sit atop gas-rich shale. “Promised Land,” directed by Gus Van Sant, is an earnest attempt, sometimes effective, sometimes clumsy, to dramatize the central arguments about fracking and its impact. Issues that have been addressed in Josh Fox’s documentary “Gasland” and in a series of articles by Ian Urbina in The New York Times crystallize in the story of Steve, a man whose ambition comes into conflict with his conscience.

Not at first, though. What is most impressive about Steve when we first meet him is that his job is also a cause. An Iowa native who watched his hometown fade away after a nearby factory closed down, he is convinced that rural life cannot be sustained by agriculture alone.

With his co-worker Sue (Frances McDormand), he arrives in a small farming town, believing that he is offering the local landowners a lifeline. Some of them, hearing the amounts his company is offering for drilling rights to their land, are eager to sign up, but Steve runs into trouble when an old-timer (Hal Holbrook) starts raising questions about what fracking will do to the water supply, the livestock and the land itself.

And then a guy named Dustin Noble shows up. He’s an environmental activist played by Krasinski, who treads the same line between awesome guy and smug jerk that he has so gracefully walked in the later seasons of “The Office.” Dustin is Steve’s rival and mirror image, a more obnoxious and more effective version of the friendly young salesman who is charming the locals with a mixture of straight talk and transparent bluff.

Fliers and posters showing dead cattle start turning up all over town, which annoys Steve. Even worse is that Dustin seems to share Steve’s interests in Alice (Rosemarie DeWitt), the pretty schoolteacher that every small town in a movie like this one must have.

It also needs a wise, almost magical geezer (that is Holbrook’s job); semi-sleazy public officials; sassy waitresses; and a lot of guys in plaid flannel shirts and trucker hats. But the nice thing about this movie is that it spends most of its running time wandering away from its native cliches, rather than wallowing in them.

Van Sant’s style of directing, watchful and low-key, puts character ahead of story, and the script invites the actors to be warm, funny and prickly. All of them — perhaps most notably, McDormand and Titus Welliver, playing a cynical store owner — are excellent company, and you can see why Steve seems to be in no hurry to wrap up his business and move on.

“Promised Land” itself, however, has a point to make, and it does so in a way that is both honorable and disappointing. It admirably tries to represent both sides of the fracking debate, even though its allegiance is clearly to the antifracking position. There is nothing wrong with such advocacy, except that in this case it means that the movie veers away from its strengths, ending in a welter of convenient (and dubious) plot twists and puffed-up speeches.

Viewers who are already skeptical of fracking are likely to find gratification in the film’s sentimental, studiously ambiguous conclusion. Those seeking scientific information will need to look elsewhere — not that rigorous science is what anyone expects from a movie. But “Promised Land” feels divided against itself, not quite sure how to reconcile its polemical intentions with its storytelling impulses, and thus finally unable to fulfill its own promise.

“Promised Land”

No star rating provided.

106 minutes

R, for language