HILLSDALE, Mich. —  When Michael Sessions ran for vice president of the Hillsdale High School student council last year and lost, he swore he’d make a political comeback.

This week, the 18-year-old senior did so in a startling way: He was elected mayor.

On Thursday, after officials reviewed each ballot, they announced — to the shock of many in town — that the teen, a write-in candidate, had beaten incumbent Douglas Ingles, 670 votes to 668.

“It’s amazing. It’s cool,” said Mike, whose four-year term begins Nov. 21. “I’m so excited, I think I’m going to be ill.”

School already has taken a back seat.

He missed homeroom Thursday to do phone interviews with Michigan rock music stations. He didn’t show up to the middle school where he volunteers as a teacher’s aide because he and his family had been whisked to New York to do the “Late Show With David Letterman.”

(On the show Thursday night, Mike reeled off Letterman’s Top Ten reasons why it’s good to be an 18-year-old mayor. No. 10 was “Parents try to tell me what to do, I raise their taxes”; No. 3 was “School bullies now have to deal with the feds.”)

His parents had called the high school principal and told him Mike was sick.

“He’s been coughing and getting over bronchitis since Saturday,” said his mother, Lorri, 42, a custodian for a sorority house. “It’s been overwhelming.”

Ingles, who owns a local roller-skating rink, declined to comment on his defeat by someone too young to have his name on the ballot during the spring primary. On Saturday, the Toledo (Ohio) Blade newspaper quoted Ingles, 51, as saying: “How much credibility does an 18-year-old have?”

Being mayor in this town of 8,200 is a part-time job that comes with a $3,600 stipend, City Manager Tim Vagle said.

Hillsdale’s day-to-day administration and operation is handled by Vagle. The mayor and the other eight City Council members make policy decisions and approve the budget. Mike won’t have an office or staff. He is required to attend two council meetings a month.

“It shouldn’t conflict with him being in school. They’re held at night,” said Vagle, 51.

Which is a good thing, Hillsdale High Principal Peter Beck said with a grin: “I told him that if he wins, he’ll still need to finish his homework…. I’d hate to have to suspend a city official.”

In late September, days after turning 18 and registering to vote, Mike walked into the city clerk’s office and filed his intention to run for mayor as a write-in candidate in this southcentral Michigan town.

His advertising budget was modest — the $700 he had saved from his summer job selling cotton candy and candied apples at local county fairs. But it was enough to pay for hundreds of business cards and 50 lawn signs.

In the three weeks before the election, Mike got classmates to help him organize public meetings and canvass neighborhoods.

“Each day after school, he would pick an area and go door to door, telling people who he was and that he was running for mayor,” said Lauren Beck, 17. “He’d talk about why he should be mayor, and had a sample of the ballot so he could show people where they had to write in his name.”

At first, residents thought Mike was doing this as a joke — or as a way to bolster his college application by adding mayoral candidate to his list of after-school activities, along with being the announcer for the high school soccer team.

Some people laughed. Others shut the door in his face. But then the mood around town shifted.

“A lot of people seemed impressed that he was working so hard,” said Brandon Thomas, 17, who has known Mike since elementary school.

The young candidate spoke at the Kiwanis Club, a record shop and the local firehouse. Hillsdale’s three-man department was sold: Convinced that the teen would help them fill a firefighter job vacant for two years, they endorsed him.

Mike even brought in stacks of voter registration cards to the school cafeteria and persuaded students who were 18 to vote, the principal said.

Lorri Sessions and her 46-year-old husband, Scott, a medical technician, said their son long had been interested in politics.

“He would watch the town City Council meetings on TV every week,” Lorri said. “He’d try to get us to join him. He found the whole process fascinating.”

A few years ago, after the automotive manufacturing plant that employed Scott left town, Lorri said, her son began talking about running for office.

The economy in Hillsdale has been slumping since several large manufacturing facilities either closed or relocated in recent years.

The unemployment rate in town hovers around 6%, and more than 10% of the population lives below the federal poverty line, census figures show.

“Here’s this kid talking about how there are grants to help towns like ours attract biotech companies,” said shop owner John Spiteri, 49. “I’m friends with Doug. He’s taught my kid to skate. But people here are hungry for anyone who can pump life back into this town. I had to vote for Mike.”

Mike, who graduates in June, has said he plans to remain in town and study political science at Hillsdale College.

The phones at City Hall have been busy since the tentative election results were announced late Tuesday, with calls from curious residents as well as pleas from at least three Hollywood studio executives who each wanted to buy the movie rights to Mike’s story.

Martha Stewart’s people have called, as have television producers from Europe and Asia who plan to cover the swearing-in.

Again and again, Vagle explained that the teenager didn’t own a cellphone and couldn’t be reached.

“I went over to Mike’s house this morning, before they left for New York, to talk to him about how to promote the town like a veteran politician,” Vagle said with a sigh. “All he could talk about was how cool it was that [rock radio station] 103.3 FM called to interview him.”

As the phone rang again, Vagle glanced at a framed photograph perched on the corner of his desk. It’s his youngest son.

He’s 21.

“If Mike wants to be a politician, this is a great place to learn,” Vagle said. “Though I thought I was done raising teenagers.”