Pete Buttigieg, the former transportation secretary and 2020 Democratic presidential candidate, announced on Thursday that he would not run for Michigan’s open Senate seat, a decision that opens the door to a 2028 presidential bid.

“My party has a deep and talented bench here in Michigan, and I am certain that we will nominate an outstanding candidate for each office,” he wrote on his Substack page, saying that “I have decided against” running in the state’s races for Senate and governor next year.

Mr. Buttigieg had been widely expected to decline to enter the governor’s race, but many Democrats had wondered if he would join the 2026 contest to succeed Senator Gary Peters, a retiring Democrat.

His decision, earlier reported by Politico, allows him to pivot more easily to the next contest for the White House — which will effectively kick off the day after the midterm elections, if not sooner. Mr. Buttigieg determined he could not run for Senate or governor and then for the White House, according to a person briefed on his deliberations, who added that the move put the former transportation secretary in prime position for the 2028 Democratic primary race.

In his post, Mr. Buttigieg made no direct mention of any ambitions for office, but he did allude to some of his political plans.

“I am simultaneously thankful to be away from Washington and yet also more motivated than ever to contribute to the future of this country,” he wrote, mentioning his desire to spend time with his husband, Chasten, and their twin toddlers.

He pledged that he would spend “more time engaging both legacy and digital media in the service of a politics of everyday life, rooted in the values of freedom, security, and democracy,” and added that he would convene “partners, allies, friends and strangers” in his efforts and engage “offline” with communities around the Midwest.

In a list that bore a faint resemblance to a campaign platform, Mr. Buttigieg also enumerated some of his priorities, including “the prosperity of the industrial Midwest, the future of our cities and towns, the condition of our infrastructure, the need for structural reform in our democracy, the outlook for our climate” as well as “the proper role of technology,” among other issues.

Mr. Buttigieg had been seen as the most prominent potential contender in next year’s marquee Senate contest, a proven fund-raiser with strong name recognition and a devoted fan base in his party.

But he also would have been vulnerable to “carpetbagger” attacks, and was plainly aware of that risk. Mr. Buttigieg, a former mayor of South Bend, Ind., became a Michigan resident in 2022, moving to Traverse City.

“I have a lot of humility about having only moved to Michigan a few years ago,” he said when asked in an interview in December about a possible run for governor there. “Although, of course, I did grow up in the neighborhood.”

Offering a preview of the qualifications he would be likely to highlight if he runs in 2028, Mr. Buttigieg pointed in his Substack post to his record as secretary of transportation. He said he lived “within short driving distance of several transportation construction projects that count among the tens of thousands now being built with funds from the infrastructure package that I spent most of the last few years working on.”

A Senate candidacy by Mr. Buttigieg would have tested voters’ appetites for elevating a member of the Biden administration. Former Vice President Kamala Harris lost Michigan to President Trump in November, and former President Joseph R. Biden Jr. was unpopular for much of his presidency.

Democrats who are eyeing the Senate race include Representative Haley Stevens, a moderate from suburban Detroit; State Senator Mallory McMorrow, who won national Democratic acclaim in 2022 with a speech defending liberal values; and Abdul El-Sayed, a progressive health director in Wayne County who ran unsuccessfully against Ms. Whitmer in the 2018 primary.

“I’ll have more to share soon,” Ms. McMorrow wrote on X.

Term limits will preclude Gov. Gretchen Whitmer from running for a third time next year, and the race to succeed her has already prompted a crowded and contentious Democratic primary. Both it and the Senate contest are expected to be competitive in the general election.

In the meantime, another Buttigieg is stepping into the spotlight in Michigan.

This spring, Chasten Buttigieg will release a children’s book whose title features the name their children use for his husband. The book, “Papa’s Coming Home,” tells of children celebrating their father’s return from a trip. A book tour is scheduled to begin in Traverse City in mid-May.