"You're not supposed to talk about it, but there's this strong undercurrent that every Christian votes Republican, and if not, you're a traitor," he says. "But how do you do that with a candidate that's not at all Christian, who's anti-Christian?"
He recounts how his temper flared during the Iowa presidential caucuses in January when he drove by some sign-wielding Newt Gingrich supporters. How could a Christian support a politician who'd been married three times, he thought.
Seyler's wife had to stop him from rolling down his window and taunting them with faux declarations of support for Obama. Another renegade impulse.
Seyler goes so far as to admit that he has a real soft spot for Obama, though he couldn't see voting for him without the president personally explaining to him how, as a Christian, he could support abortion rights and gay marriage.
And yet because he's a believer, Seyler says, he can appreciate better than secular voters how Romney's religion would shape presidential decisions.
"If it came down to policies, I'd probably go with Romney," he says. "But politics isn't as big to me as beliefs. Beliefs are who someone really is."
Seyler didn't come by his piety easily.
In high school, he grew so disenchanted with what he saw as the shallow, sterile faith of some teachers at his Christian high school that he thought about killing them. He and a friend -- a pastor's son -- even mapped out an attack in study hall one day, listing the guns and ammo they'd need.
They abandoned the plan once the bell rang. But Seyler came much closer to killing himself. He was feeling insecure and unfulfilled, hung up on his introversion and his acne and crooked teeth, and he wasn't sure anyone really loved him.
"I had my finger on the trigger, and I clipped off the safety," he recalls, sitting atop a student desk in his high school classroom. "I got some towels and spread them onto the carpet so my mom wouldn't have to scrub the blood."
He was 15 or 16, alone at home in his room. "I had the gun in my mouth."
Then his father knocked on the door.
That interruption and a string of other developments that Seyler would later interpret as divine interventions restored his Christian faith. But only after a long season of searching that included exploring other religions, including Islam.
At around the same time, his father sent him to join a missionary team in Peru. There, in the jungle, he discovered a raw, real faith that he hadn't seen back home. "The joy in Christ that I saw in the Peruvians, even though they had nothing -- that's what hooked me on a life in ministry," he says.
Now, though not technically a minister, Seyler spends his days pastoring to kids from his perch in the classroom. And after class, he's constantly talking to students and former students by text and Facebook, fielding questions about school, dating, existential angst -- you name it.
Seyler says that intense outreach is propelled by his own teenage struggles and by his commitment to living the kind of faith he saw in Peru and felt missing in the Christian high school of his youth. He keeps a second Marilyn Manson picture in his Bible -- one showing the singer as a sweet young boy -- to remind him "not to refuse people who are crying out for help."
At an adult Bible study that meets Sunday mornings before services, Seyler answers a prayer request from a middle-aged couple whose son recently attempted suicide at his military base in Texas. He had been in touch with Seyler, his old Bible teacher, just a couple weeks earlier.
"Thank you, God, for the opportunity to come boldly and thankfully to your throne," Seyler says aloud to a roomful of bowed heads. "I pray for Chad. I know you live inside of him. Help him to embrace truth and to reject the lies that he's believing."
Afterward, in the hallway, Seyler explains that he'd advised Chad to take baby steps in his faith, to find a church and some likeminded believers. "This kid has been partying, clubbing a lot," he says. "People have been a bad influence on someone who wants to be a man of God."
To Seyler, Chad's problem is living too much in the world when he should be handing his life over to God.
It's an old-school message that you might not expect to go over well with teens and 20-somethings. But Seyler's emotional availability has made him a local celebrity.
He's at school a couple weeks before the kids return, painting hallways for extra income, when three teenage girls peel off from volleyball practice in the gym to chat up their favorite teacher.
"He's like a friend," one says. "You can go to him with your problems, and he doesn't judge you."
But being what Seyler calls a "radical" and a "follower of Jesus" also comes with plenty of costs -- like supporting six kids on a parochial schoolteacher's salary.
His wife, Kim, may have a Keurig single-cup coffeemaker in her kitchen, but she found it used on Facebook and insists on reusing the grounds in the K-cups before tossing them. She picks up babysitting and housecleaning gigs to supplement their income. Eating out means fast-food joints like Fazoli's or Tasty Tacos, a Des Moines chain.