MANKATO — Mankato schoolteacher Tim Walz won a shocking victory Tuesday night over six-term Congressman Gil Gutknecht, becoming the first Mankato resident in a century elected to Congress.

Walz, making his first run for political office of any kind, toppled the 12-year veteran Republican and prompted a raucous celebration among southern Minnesota Democrats packed into a Mankato Holiday Inn ballroom.

A geography teacher at West High School, Walz said the campaign proved that average Americans can still change the country.

“The belief in America is that you can rise up and do this,” he said. “So this, to me, is incredibly gratifying.”

With 87 percent of precincts reporting just after 1 a.m., Walz had 52 percent of the vote to Gutknecht’s 48 percent. By then, congratulations were pouring in from around the country, including Congressman and Marine Corps veteran Jack Murtha, who had a short message for Walz — a 24-year veteran of the Army National Guard.

“Jack Murtha just called and said ‘Semper Fi,’’’ Walz said.

For Gutknecht, the end of his congressional career came the same way it began — on a wave of voter disgruntlement with the way the ruling party was doing its job. He was part of the freshmen class in 1994 that allowed Republicans to take control of an increasingly corrupt Democratic Congress after nearly 40 years of one-party control.

In 2006 it was the Iraq war, the scandals that have rocked the GOP-led Congress and repeated federal budget deficits. Also contributing to Gutknecht’s struggles was dissatisfaction, particularly in Rochester and Mankato, with the way a $2.3 billion federal loan was made available to the Dakota, Minnesota and Eastern Railroad project that intersects the district.

Gutknecht couldn’t be reached for comment at 1 a.m., but spokesman Bryan Anderson said he had conceded the race.

“He was thankful for the people of the 1st District letting him represent them for 12 years,” Anderson said. “He’ll dust himself off and move on to the next thing.”

The evening started much better for Gutknecht, who had a slight lead in early returns. During a stop in Mankato at around 8 p.m., he predicted victory to local Republicans and said he thought the GOP would defy political pundits who prognosticated they’d lose control of the House.

But he admitted it had been a tough race.

“It’s been a combination of a heavyweight fight and marathon,” he said. “But it’s lasted about six months.”

At the Holiday Inn, hundreds of Walz supporters appeared to be feeling both optimism and nervousness. That changed at 10:04 p.m. when the big screen TV at the front of the ballroom showed the 1st District race dead even and the crowd let out a thunderous roar.

Gutknecht — after winning comfortable victories in his last four elections and going undefeated in 15 previous elections for state House and congressional seats — was soon trailing and he never regained a lead as more and more votes came in from across southern Minnesota.

It was a remarkable turnaround from a year ago when Walz was viewed by many as just another Democratic sacrificial lamb running against a long-term incumbent — one who had steadily grown his margins of victory over increasingly less-experienced and under-financed opponents.

With no previous elected experience and no money, Walz expressed frustration at the beginning of the campaign that he couldn’t even get interviews with some media outlets in the Rochester area. And Gutknecht campaign officials, along with Gutknecht himself, consistently discounted Walz as a serious threat.

By fall, however, everything had changed. Walz had been relentless in raising campaign funds — eventually topping $1 million — and campaigning across the sprawling district with his message of desperately needed change in Washington. He was getting nationwide attention and his corps of volunteers, including many young people who had once been his students, seemed endless.

Ever the teacher, Walz said early Wednesday he was certain those dozens of 20-something volunteers had learned a lesson about democracy this fall.

“Every one of those kids is going to change the world,” he said. “They know it can be done now.”