His yet-to-be-declared candidacy is already highlighting the enduring fractures over President Trump in this heavily Mormon state, where voters have long been uneasy with Mr. Trump’s conduct. At issue is whether Mr. Romney, the 2012 Republican presidential nominee, should be an overt check on the president, and even use a Senate platform to mount his own White House comeback, or act as an ally and retain access to Mr. Trump the way Mr. Hatch has done.
Mr. Trump won Utah but garnered only 45 percent of the vote, the lowest of any Republican nominee for nearly a quarter-century. The state’s largely conservative voters found his coarse language, treatment of women and contempt for many immigrants and refugees to be anathema to a faith centered on rectitude and forged by exile. About 27 percent voted for Hillary Clinton, and 21 percent voted for Evan McMullin, a Mormon political neophyte who ran as a conservative counter to Mr. Trump.
Utahns saw Mr. Trump as a far cry from his predecessor from four years earlier.
Strolling between buildings at the State Capitol complex, the imposing Wasatch Range looming in nearly every direction, Lt. Gov. Spencer J. Cox sought to explain why Mr. Romney is so formidable that nearly every ambitious major Republican, including himself, is standing down.
“We have a little bit of an inferiority complex in the state of Utah,” Mr. Cox said. “I think it has to do with how we got here. We got kicked out of the country, basically. There was an extermination order. And so we came out here with nothing.”
Gesturing to the elegant State Capitol and booming city at the foot of the mountains, he said, “This was a barren place, and we turned it into this.”
The Romney ancestors were part of the story, back to 1837, when a carpenter named Miles Archibald Romney heard a missionary tell the story of Joseph Smith, Mormonism’s founding prophet.
And because Utah leaders are determined to put on the best face for their state and their church, Mr. Romney’s image is far more important than the particulars of his residency. “All-American family, all-American business acumen, elected governor, ran for president in a respectful way,” as Mr. Cox put it.
A sixth-generation Utahn who will say only that he did not vote for Mr. Trump or Mrs. Clinton, Mr. Cox all but encouraged Mr. Romney to be a voice of opposition when needed.
“I think if he wants to be a check, it won’t hurt him here like it has others,” he said, noting the Republican lawmakers who have been politically damaged for their criticism of Mr. Trump, such as Senators Jeff Flake of Arizona and Bob Corker of Tennessee, both of whom are retiring. “He could do it from Day 1 and he’d be fine.”
Some Republicans here see Mr. Romney’s ascent to the Senate as only the first step. Mr. Herbert said he “can accelerate” and become Senate Republican leader. Daniel Hemmert, a state senator who last year began a Draft Romney effort, went further, suggesting that if Mr. Trump is damaged or does not run again in 2020, the party should turn to the freshman senator from Utah.
Mr. Romney “has to be at the top of that list,” Mr. Hemmert said.
That is precisely why Mr. Trump aggressively wooed Mr. Hatch to run for an eighth term, even flying the 83-year-old senator out to Salt Lake City last month, hoping to block Mr. Romney’s return.
Mr. Trump and Mr. Romney ferociously attacked each other in 2016. Mr. Romney called his successor “a phony, a fraud.”
Returning fire, Mr. Trump deemed Mr. Romney “a choker” who “walks like a penguin.”
There was a brief détente when Mr. Romney was considered for secretary of state after the 2016 election.
But after last summer’s violent white supremacist marches in Charlottesville, Va., Mr. Romney demanded that the president apologize for his equivocal response, saying that “what he communicated caused racists to rejoice, minorities to weep, and the vast heart of America to mourn.”
Mr. Trump telephoned Mr. Romney in recent days, and they had a pleasant conversation, according to two White House officials, but, they added, the president did not explicitly offer his support.
Many Republican leaders here are hopeful that the former antagonists can find common ground.
“I think there is a willingness on both sides to say, ‘Look, we may disagree on stuff, we may have problems from our past, but what we ought to be looking toward is our future,’” Mr. Herbert said.
Yet to Mr. Trump’s most vocal supporters — and they exist here as in any state — simply trying to get along is insufficient. The State House speaker, Gregory Hughes, a Pittsburgh transplant, like Mr. Hatch, who practices what he calls “brutal honesty,” said bluntly, “I hope and actually I expect Governor Romney to be an ally of the president and the policies he’s pursuing.”
Mr. Hughes boasted of his early support for Mr. Trump and noted that he had gotten to know the president’s eldest son. He also praised Mr. Romney: “We joke maybe only Jesus can beat him.”
But Mr. Hughes came away stunned from a private meeting late last year with Mr. Romney, who seemed unaware that the protests by National Football League players during the national anthem had contributed to the league’s woes with fans, according to a Republican to whom Mr. Hughes mentioned the conversation. It was, to the speaker, an indication that Mr. Romney remains somewhat insulated by his wealth.
The contrasting expectations for how Utah Republicans want Mr. Romney to handle Mr. Trump reveals not only the fault lines of the party as it eyes the 2020 race for governor (Mr. Cox and Mr. Hughes are both considering campaigns for the open-seat race) but also the nuances within the church over how differently Mormons view the president.
And while Mr. Romney is not expected to face a competitive race in the general election, the demographics in this state are changing as non-Mormon transplants move in and some natives drift from the faith of their families.
Jenny Wilson, whose father once ran against Mr. Hatch, reflects this shift. A member of the Salt Lake County Council, Ms. Wilson is the likely Democratic nominee in the Senate race. She was “baptized Mormon,” as she put it, but is no longer active in the church.
The overwhelmingly white, Republican and male power structure of the state is outdated, she argued.
“My interest in running for office is about offering a different voice,” she said, noting that there were no Democrats in the state’s congressional delegation.
In the slope-side lobby of the St. Regis resort in Deer Valley last weekend, a mix of Utah and Washington contributors gathered for a ski fund-raiser for Mr. Hatch, the proceeds of which may eventually find their way to a political institute he plans to build.
Not far from the hot-chocolate bar, Mr. Hatch, clad in a patterned ski sweater, helped hand out Olympic-medal-style awards to participants.
Most everyone in attendance expected Mr. Romney to run. And Gordon Smith, a former moderate Republican senator from Oregon who is from a prominent Mormon family, crowed a little over how the only apparent impediment had been swept away: the defenestration of Stephen K. Bannon, who had harshly criticized Mr. Romney.
“I always figured if he ran, Bannon would try to beat him,” Mr. Smith said, before adding with evident relish, “Well, that’s gone.”