Duluth's popular mayor announced on social media Sunday morning that he will not seek a third term in office.

Don Ness, often credited with helping to steer a renaissance in the industrial port city, will finish out his second four-year term in office next year, according to his posting on Facebook. The announcement ended months of speculation in the Lake Superior port city of 86,000.

"I've tried to do this job well and I know the next person to hold the job will do the same," Ness wrote. "If I thought for a moment that my role was necessary for our continued success, I would run again. But it's not. The progress we've made as a city continues because it's based on the strengths of our city and efforts of thousands – the mayor is just one of many."

Ness, 40, did not detail any future plans and said he would not be available for comment Sunday. He had said previously that he has no aspirations for higher office and disliked political game-playing.

The first mayor to run unopposed since the city was incorporated in 1887, Ness often took to social media to communicate the city's residents. There, he questioned months ago whether he would run again, saying that although he had never enjoyed the work more, he was struggling to generate enthusiasm for the political side of the job.

"Turnover in the mayor's office is a healthy thing" he wrote in July, adding that "If you do it right, it's not a job designed for longevity — you get stuff done and then you get out of the way."

The second-youngest person ever elected to the Duluth City Council at age 25, Ness grew comfortably into the helm at city hall, where he garnered support from business and labor groups alike. At one point in 2011, he enjoyed an 86 percent approval rating.

Ness appealed to a young demographic that he targeted in rebuilding the city's image by promoting music, arts, and entrepreneurial endeavors such as craft breweries. He and others have aimed to capitalize on the city's natural hillside beauty by promoting its parks and trails for hiking, mountain biking, paddling, skiing and other outdoors activities.

Ness once stage-dived with Minneapolis Mayor R.T. Rybak at First Avenue in Minneapolis to celebrate a new album from Duluth band Trampled By Turtles.

Recently, he has been championing an effort to revitalize the city's long-neglected western end. He has been promoting investments aimed to make the area along the St. Louis River corridor a second, outdoor sports-emphasized tourist destination, behind popular Canal Park near the Lake Superior shipping port and iconic lift bridge.

Ness said he hadn't aimed to get into politics while growing up in Duluth, raised by an evangelical pastor father and social worker mother.

At the University of Minnesota Duluth, he was elected Student Senate president and became active in the DFL, later running the re-election campaigns of U.S. Rep. James Oberstar.

Ness said in a 2012 Star Tribune profile that he'd always been a little awkward and "too boring" for higher office, joking then that "I have the nerd vote locked down."

The mayor wrote Sunday morning that he planned to turn off his phone and head to the woods with his wife and three young children after posting his announcement, and would not be available for comment.

Pam Louwagie • 612-673-7102