Political unknown Kurt Bills turned up the heat on U.S. Sen. Amy Klobuchar on an already sweltering day at the Minnesota State Fair on Thursday, debating how to shrink the federal debt, get things done in Washington and apportion credit for killing terror chief Osama Bin Laden.

"It was our troops over there and our president's leadership and willingness to take a risk, that was how we killed Osama Bin Laden," Klobuchar said.

"How we killed Osama Bin Laden was a bunch of Navy SEALs killed him," shot back Bills, a GOP legislator hoping to unseat the incumbent Democratic. "Don't take credit for it!"

"Rep. Bills, please!" she replied. "I said it was our troops that did the job, and we needed our troops there to get that done."

In the hourlong joint appearance, Bills did not manage to poke Klobuchar off message. But he, and his booing, mocking fans, did manage to rankle the first-term senator during the debate sponsored by Minnesota Public Radio.

Until Thursday, Klobuchar, who has vastly superior campaign coffers, polling numbers and base of support, has largely been content to ignore her underfunded challenger and continue concentrating on Senate work, with weekend parade appearances thrown in.

But she got right in the mix with Bills at the fair, which could be a sign of a testier race to come.

"We both agree we need to reduce the debt. There is absolutely no doubt about that. Do you want to go for a plan ... [that] eliminates the Department of Energy, Department of Education?" Klobuchar asked. She paused, seemingly taken aback as Bills fans cheered the idea, which Bills has supported.

Bills, a first-term state representative and high school economics teacher, held his own and tested out some new lines.

He excused his paltry fundraising by challenging hers -- and that of every other politician who has raised significant campaign cash.

"You don't get a whole lot of money in when you talk like me that there shouldn't be those bailouts, that those millionaires shouldn't get richer, that crony capitalism is now running our country," he said, noting his support of a flat tax.

"This election is really not Republican versus Democrat any more; it's America versus Washington, D.C.," he shouted.

Klobuchar fought back.

"I think our priority should be helping the middle class," she said, adding that she would support rolling back tax cuts on those making more than $250,000 a year to pay down the debt.

A fight over records

She cited her long list of bipartisan work on veterans issues, business competitiveness and debt reduction as examples of the way forward. She contrasted that work with Bills' state House proposal, which went nowhere, to make gold and silver legal tender in Minnesota.

To hoots and hollers from Klobuchar's fans in the crowd, she said: "I'm sorry, Rep. Bills, but you haven't passed one bill that even got signed into law."

He countered that he offered a measure for tax credits for employers who hired veterans, but DFL Gov. Mark Dayton vetoed it. Bills suggested during the debate that Dayton and Klobuchar were "colluding" on that veto.

In fact, that bill never passed the Minnesota House but was woven into a larger tax measure, which contained many provisions that Dayton said he opposed because they would cut taxes for businesses more than those for homeowners.

Bills came to the race, which higher-profile Republicans avoided given Klobuchar's might, on a wave of support from Ron Paul fans.

This week, rather than attend the Republican National Convention in Tampa to which he was elected as a delegate, he chose to stay in Minnesota. He is hoping that shaking hundreds of sweaty hands and munching food on a stick will help him in his quest to unseat Klobuchar.

Romney support draws fire

It might be just as well that he is staying away from Tampa. The Paul-dominated Minnesota delegation did not appreciate Bills' recent endorsement of Mitt Romney.

"I feel like he betrayed the Ron Paul movement," said Yelena Vorobyov, a delegate from Apple Valley.

Although she said she didn't understand Bills' decision to support Romney the week before the convention, she still said Bills represents her values.

"He's conservative, he's a school teacher and he understands economics," she said in Tampa.

Klobuchar's strengths include support from the businesses community and polling well not only with Democrats but also independents and even some Republicans.

"I've got the feeling that she really cares about the people of Minnesota," said Gary Elmstedt, who showed up at the State Fair debate wearing a Klobuchar T-shirt. The St. Paul man, who said he tends to vote for Democrats but ticked off Republicans he's supported as well, returned to the State Fair after three decades away to support Klobuchar.

He said she has responded to his needs when he has contacted her office.

"She pays attention to your particular question," Elmstedt said. "I think she's a people person."

Staff writer Baird Helgeson contributed to this report. Rachel E. Stassen-Berger • Twitter: @rachelsb