A year after Tim Walz gained national attention as Kamala Harris’s running mate, he announced on Tuesday that he would seek a third term as governor of Minnesota.

Mr. Walz, who has signaled interest in a presidential run in 2028 by speaking at Democratic conventions in two states, has said that a new term as governor would close the door on a White House bid in two years.

If Mr. Walz, 61, is re-elected in 2026, he would be the first governor in Minnesota history to win a third consecutive four-year term.

For now, Mr. Walz is seen as unlikely to face a strong Democratic challenger, but political analysts say an unusually strong field of Republican rivals is taking shape.

In a video announcing his new bid for governor, Mr. Walz alluded to the challenges the state has faced this year, including an attack on lawmakers that killed the former speaker of the Minnesota House and what he described as the “chaos, corruption and cruelty coming out of Washington.”

“We have to come together,” the governor said in a video his campaign released Tuesday morning. “We can’t lose hope, because we’ve seen what we can do when we work together.”

Mr. Walz, known over six terms in Congress as a moderate Democrat who was willing to work across party lines, enters the race with significant advantages and liabilities.

Mr. Walz holds deep institutional support as an experienced campaigner with a vast network of donors and supporters after two decades in elected office. And in Minnesota, Republicans have not won a statewide race since 2006, when Tim Pawlenty narrowly won re-election to the governor’s office.

But Mr. Walz’s track record as governor and his vice-presidential run have diminished his reputation as a moderate, which had made him appealing to voters in rural parts of the state.

As conservatives hope to win the governor’s mansion, they are blaming Mr. Walz for the state’s fiscal problems, including a nearly $6 billion deficit that the state is projected to face as early as 2028. They also blame him for the state’s failure to prevent fraud schemes that have targeted safety net programs run by state agencies.

“Minnesotans have looked at our state, they’ve looked at what has happened and they have said, ‘Enough,’” said Lisa Demuth, the speaker of the Minnesota House and the top Republican in the Legislature. “In 2026, I think a Republican governor is exactly what is needed.”

In an interview late last month during the opening day of the Minnesota State Fair, Mr. Walz seemed inclined to seek a third term.

But he said he had been speaking to people across the state in recent weeks to get a clear sense of how Minnesotans were feeling about him.

“None of us are owed these jobs,” Mr. Walz said. “You’re a servant leader, and if the people of Minnesota want you to serve and it’s the appropriate time, then you do so.”

Mr. Walz, who was raised in a small, rural town in Nebraska, worked as a public-school teacher for nearly two decades before unseating a Republican incumbent in Congress who had long represented a red-leaning district.

Mr. Walz held on to the seat even as the district became increasingly conservative, and he leaned on his image as a centrist with working-class roots to win the governor’s office under the motto “One Minnesota” in 2018.

In Mr. Walz’s first term, he imposed strict lockdowns during the pandemic, drawing criticism from President Trump and protests outside the governor’s mansion.

Weeks later, unrest and vandalism spread through Minneapolis after a police officer killed George Floyd, setting off a national reckoning over policing and racism. Mr. Walz faced criticism for not deploying the National Guard until scores of buildings had been burned.

Still, Mr. Walz easily won a second term in 2022, and Democrats won control of both state legislative chambers and the governor’s mansion for the first time since 2014.

With a trifecta, Mr. Walz and fellow Democrats passed numerous liberal bills, expanding abortion rights, legalizing recreational marijuana, funding free school meals, forcing employers to provide paid medical and family leave, tightening gun restrictions and protecting transgender minors who traveled to the state for medical care.

U.S. Representative Betty McCollum, a Democrat, said the 2023 and 2024 legislative sessions showed Mr. Walz’s willingness to act boldly when he had political capital to spend.

“He accomplished a lot of great things that I wish we were doing in Congress,” she said.

But Republicans said the Democrats’ policies, passed with a narrow majority, swung the state too far to the left and set the stage for a looming deficit. That will force the next governor to make painful cuts, they said.

Minnesotans have expressed growing consternation about fraud schemes targeting safety net programs run by state agencies. Federal prosecutors have said that people have stolen as much as $1 billion since 2020 by submitting bogus claims to state agencies overseeing food, housing and other aid programs.

Mr. Walz, critics say, failed to hold anyone accountable for inadequate safeguards that allowed fraud to continue.

“It will be one of the top campaign issues because we have a budget deficit and taxes in Minnesota are high,” said State Senator Jordan Rasmusson, a Republican who represents a largely rural district in western Minnesota. “Minnesotans are generous, but I don’t think they are going to tolerate more of their tax dollars going to criminals.”

Mr. Walz said his administration had taken steps to curb fraud, much of which he said unfolded as money was being disbursed quickly during the pandemic.

“There’s a big difference between fraud and corruption,” he said. “This is criminals being caught, just like if they steal from your house.”

Asked about the role he might play in helping Democrats win back the White House, Mr. Walz said he intended to call out policies by the Trump administration that he considered “cruel” and “illogical.” To win, though, he said, Democrats must find a way to “bring a politics of hopefulness.”

Jaime Harrison, who served as the chair of the Democratic National Committee from 2021 until February, said that whether or not Mr. Walz served a third term as governor, he would make a strong presidential contender in 2028.

After Mr. Walz made an initial splash on the campaign trail last year, Mr. Harrison said he felt the Harris campaign kept the governor “handcuffed a little bit,” which he said may have been a mistake.

“I think one of the things that people will look for in the 2028 is authenticity, people who are willing to roll up sleeves and fight,” Mr. Harrison said in an interview before the announcement. “I believe that Tim Walz is that type of leader.”