“Jesus Camp” doesn’t try to explain why Evangelical Christians are a millions-strong group. Filmmakers Heidi Ewing and Rachel Grady instead focus on a strange, intense part of this massive movement. The results are frightening, but it’s only a small slice of a morally and politically complicated phenomenon.

Ewing and Grady say they set out to make a movie “about kids of great devotion and faith.” Then they found Becky Fischer. Fischer is a Charismatic (similar to a Pentecostal) children’s preacher who runs a camp called “Kids on Fire.” A charming but steely speaker, Fischer can joke with her youngsters one minute and make them cry the next. Her preaching style is upbeat and ingenious – she uses toys and hip-hop to rail against secular culture.

Charismatics speak in tongues, and the prayer sessions are shot like a horror movie: all extreme close-ups of little heads and crying eyes set to a throbbing soundtrack. However, the devoted young Christians that the filmmakers focus on don’t need this creepy camerawork to be compelling.

They’re much more interesting when they speak for themselves. Sweet and spacey Rachael is constantly trying to convert strangers even as she struggles to articulate her thoughts. Tory is a dancer who worries that she’s doing it “for the flesh.” Levi – a bright kid who references Galileo when talking about the tension between religion and science – dreams of being a preacher.

“Jesus Camp” says 42 percent of evangelicals are “saved” before they turn 13. One young camper says he became born again at the wise age of five. Over and over again, the adults say that this generation will be a defining one in America. “We’re kind of trained to be warriors, but in a fun way,” Rachael says. At one church event, the children perform a spiritual march wearing face paint and camouflage, and a counselor chants “This means war!”

“[Children] are so usable in Christianity,” Fischer says, with no trace of shame. When she talks about Iranian children memorizing the Koran, she’s not bemoaning indoctrination; she’s admiring the competition. Her brand of fervor is justified, she explains, “because we have the truth.”

Parents make sure their kids “stay on track” by home-schooling them in creationism, taking them to anti-abortion rallies and sending them to camps like the one Fischer runs. Ewing and Grady explain that many of them belong to dance classes and baseball teams where only home-schooled children are allowed.

The mini-mission of the film is a trip to D.C. to pray for the confirmation of Samuel Alito, a reminder of the political ramifications of this passion that threads through the film. Ewing and Grady also follow some of the kids to Ted Haggard’s mega-church in Colorado Springs, Colo. Haggard meets with President Bush every Monday. In one scene, church members pray for a cardboard cutout of the President.

The main flaw of “Jesus Camp” is that it strays from its fascinating subject too often. Footage of the campers is punctuated by radio broadcasts from Air America’s Mike Papantonio, but he’s hardly able to tear apart this world with a few angry rants. The people who will see “Jesus Camp” don’t need to be told that evangelism like this is dangerous, that it goes against Christian values, that politicizing religion destructs it. They already think that and more; if they don’t, Papantonio won’t change their minds.

Neither will “Jesus Camp,” although the filmmakers hope moderate Republicans will be moved by what they see. Fischer herself was happy with the film. As for what other people will think, she says at the end: “Some extreme liberals who look at this should be shaking in their boots . . . ‘Oh my goodness. I didn’t know this was possible. What will these kids be like when they grow up?'” Then she smiles.