The Monday after he clinched the Republican endorsement to run for U.S. Senate, Kurt Bills was in the classroom, not on the campaign trail.

The campaign against heavily favored Democratic incumbent Sen. Amy Klobuchar could wait. Media interviews could be slotted in around the end-of-semester business of collecting textbooks and organizing the senior dodgeball tournament between the AP economics and AP chemistry classes.

Bills is building his campaign around the message that he's just a high school economics teacher who wants to bring Econ 101 to Washington. But first he wants to wrap up the economics lessons he's been delivering all year at Rosemount High School.

"Once the summer vacation hits, my family and I are committed to touring around the state," said Bills, who has retrofitted a big blue school bus as his campaign vehicle.

For national political observers, Bills' campaign is beyond a long shot. The first-term state lawmaker was swept to GOP frontrunner status on a wave of support from fellow backers of libertarian icon Ron Paul. But Klobuchar has the highest approval ratings of any politician in the state and $5 million in the bank. Bills' campaign, by contrast, started April with $33,000 cash on hand.

"This is not a race that's on anyone's radar," said Jennifer Duffy of the Cook Political Report, which lists Minnesota firmly in the "solid D" category for the Democratic incumbent. "Nobody sees a lot of vulnerability for Klobuchar [against this] opponent who isn't very well known."

But Bills walked the halls of Rosemount High School with a broad smile on his face Monday morning, stopping to accept hugs and congratulations along the way to his 7 a.m. advanced-placement economics class. He was out-spent by the establishment-favored candidate in the endorsing contest, so he's used to the underdog label.

"If you want to write a diatribe against me, I completely understand and it's probably well deserved," Bills joked with his students as he urged them to fill out an evaluation of the year's lessons in micro and macroeconomics. He also asked them what he could improve on next year -- just in case he's not on his way to Washington.

"Think all way back to the beginning," Bills asked students. "What worked in the course? What was good for you, what was bad for you?"

This being an advanced-placement class, the students agreed that what Mr. Bills' class really needed was more quizzes, and steps to ensure that students who didn't do the required reading couldn't fudge the answers in class.

Their suggestions pleased their teacher. "You've got to hold them accountable, and the only way to hold them accountable is a quiz. That's something we study, moral hazards," Bills said.

Bills' students and former students have turned out to volunteer for his campaign and have tracked his political career with interest as he ran first for local office, then the state Legislature and now the U.S. Senate, all in the space of a few years.

But while Bills sometimes draws on his political experiences to make points about economic principles, senior Alex Luing said his teacher keeps politicking out of the classroom.

"He makes a very clear point to make sure he doesn't bring any personal opinion into the classroom experience," Luing said. "He's energetic. Him being energetic helps us learn the material a lot more than a normal textbook would. He's able to go beyond the textbook and use what he's learned."

Bills once used the Rolling Stones to drive home the important macroeconomic principle to his students that "You Can't Always Get What You Want." He's also been known to put on some tunes from rocker Van Halen and shout the lesson over the guitar solo, or invite students to jump up and do victory laps around the room when they get an answer right, or do the wave back and forth around the classroom, just to keep things interesting.

"He's a really quirky guy," said senior Sara Devitt, who popped her head into the room before class to congratulate Bills on the weekend convention results. "Econ doesn't sound very fun. ... But he's so good at balancing the fun with econ, keeping it upbeat and keeping it very positive.

"He's the best teacher I ever had," she said.

Jennifer Brooks • 651-925-5049