TOPEKA, Kan. — For more than six years, Gov. Sam Brownback has steered Kansas on a hard right turn on one issue after another: taxes, guns, abortion rights, Medicaid and welfare benefits.

He will leave as an unpopular leader of a state in uncertain fiscal health, with more robust conservative policies and governed by a Legislature in which many in his own Republican Party have defied him. Polished, persistent and self-assured, Mr. Brownback has been seen as a model for the opportunities and perils of governing without compromise from the right on both social and fiscal issues.

But after the Trump administration said on Wednesday that Mr. Brownback, 60, would be nominated to serve as an ambassador at large for international religious freedom, his legacy in Kansas may be a cautionary note that even in a Republican state, there are dangers in governing too far to the right.

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“He puts the lie to the myth that the default strategy is just to go as conservative as you possibly can in Kansas,” said Chapman Rackaway, a longtime observer of Kansas politics, now at the University of West Georgia.

On Thursday, standing beneath a buffalo head mounted on the wall of his office, Mr. Brownback was by turns contemplative, jovial and emotional as he announced that his time as governor would be coming to an end. For about the first five minutes, he listed what he felt were his accomplishments, including a sustainable water plan for western Kansas farmers and the growth of the state’s wind energy industry.

Still, the rollback of his signature 2012 tax cuts by the Legislature last month, a stinging rebuke, hung heavy.

“I’d like to have kept the income taxes lower,” Mr. Brownback said. “And I’d like to have kept the business tax deduction.”

Yet he remained defiant to the criticism that his tax policies had left the state with huge budget deficits. Asked if he should have approached his tax policies differently, he largely blamed a weak national economy for the state’s fiscal woes.

“If there’s one thing I could change, it’d be the price of oil and the price of wheat,” he said. “We hit a recession in ’15.”

Mr. Brownback’s nomination is something of an anticlimactic turn for a figure who once sought to cut a path from the Iowa caucuses to the White House, and then reinvented himself as a tax-slashing activist governor.

Viewed last year as a prospect for President Trump’s cabinet, Mr. Brownback will settle instead into a low-profile diplomatic post with no particular political clout.

Still, in his remarks, he spoke fervidly of his new role. At one point, explaining how taking communion could get people killed in some countries, Mr. Brownback, who is Catholic, became red in the face, paused and had to take a sip from a Styrofoam cup before continuing to speak.

In some respects, the position may be a return to an earlier version of Mr. Brownback’s political persona: During his time in the United States Senate, he was known chiefly as an articulate and well-mannered advocate for conservative social issues, like opposing abortion and human cloning, and for speaking out on issues of international human rights.

Bob Vander Plaats, an evangelical activist in Iowa, said that when Mr. Brownback ran for president in 2008, he was not viewed as the tax-cutting crusader he turned out to be as governor.

“Not that lowering taxes wasn’t important to us, but he was always seen as a pro-family candidate,” said Mr. Vander Plaats, who backed Mike Huckabee that year.

To critics and allies alike, Mr. Brownback’s fatal flaw might have been his unyielding devotion to his conservative tax doctrine.

He argued that Kansas should be more like Texas and Florida, states without income tax — though he barely addressed the concerns of people who said that those states had other major revenue generators in oil and tourism.

Dan Hawkins, a Republican state representative, has been a close ally of Mr. Brownback’s over the years. He said the governor “has had an extremely successful administration,” pointing to things like welfare overhaul and privatizing the state’s Medicaid system.

But Mr. Brownback’s tax policy was his downfall, Mr. Hawkins said.

“Maybe the governor was out there a little bit on his own, away from mainstream Kansas on his tax policy,” Mr. Hawkins said. “That’s maybe why you have the backlash. To demonize him over it is wrong, too. What he wanted was laudable. He wanted growth for Kansas.”

The governor’s stubbornness in sticking with conservative orthodoxy on taxes was in some ways counter to his more pragmatic approach in other areas.

He recently toured the state’s western reaches to promote conservation measures for the Ogallala Aquifer, the nation’s largest freshwater aquifer, whose depletion could be detrimental to Kansas’ vital agricultural economy.

And he has been generally supportive of providing financial incentives to renewable energy providers as a way of boosting Kansas’ wind energy industry.

His expected successor, Lt. Gov. Jeff Colyer, a plastic surgeon from suburban Kansas City, has been a close supporter of Mr. Brownback’s policies and is viewed as unlikely to reverse course.

And allies, like State Senator Ty Masterson, a Republican, praised the governor’s accomplishments, saying Kansas had gone from “an abortion state to a strong anti-abortion state, and from a high-income-tax to a low-income-tax state.”

“It is true our state government had some hard spending choices to make with the slower tax revenue growth, but our people had more money in their pockets, until this year, when the new Legislature overrode his veto and gave that hard choice back to our constituents,” Mr. Masterson said.

To Steve Brunk, a former Republican state representative, Mr. Brownback’s reputation was hurt by what he felt were distortions about the impact of his tax policy and state spending.

He said that lawmakers under Mr. Brownback increased funding for schools — though education advocates argued that those increases did not keep up with inflation, and the costs of supporting growing school populations.

Mr. Brunk also pointed to legislation passed in 2015 that increased consumption taxes — on things like cigarettes and the sales tax — and closed tax loopholes as ways that the governor was working to help right the state’s finances.

“In my mind it was just a matter of waiting for the economy to recover,” he said. “We believe now that it is recovering. And so the tax cuts that are in place would do a lot to stimulate the economy.”

Others, including many Republicans, saw less to praise. State Representative Stephanie Clayton, a moderate Republican, said she was “excited” about Mr. Brownback’s likely departure and called it “an opportunity for Kansas to have a fresh start, for us to return to dignity in governing.”

Ms. Clayton said the governor’s tenure had been marked by division within the Republican caucus and political hostility toward moderates like her.

But Ms. Clayton said she did not doubt that Mr. Brownback was genuine in his conservative beliefs.

“The man was not insincere. He believes what he does,” Ms. Clayton said. “He wasn’t just doing it for political benefit.”

On the Christian right, his nomination was applauded. “In his time in the United States Senate, religious liberty was one of his top priorities, not only for Christians but for religious minorities around the world,” said Gary Bauer, a prominent Christian activist.

Aaron Estabrook, executive director of the Save Kansas Coalition, which has criticized Mr. Brownback and advocated political moderation, said he was “relieved” to know the governor was moving on.

“I think good leaders acknowledge mistakes, and they adjust,” Mr. Estabrook said, “and he just never did that.”