Darin Smith says he remembers January 6 very differently from Liz Cheney and her congressional colleagues investigating the US Capitol riot.

“People were singing patriotic songs, the national anthem, hymns,” insists Smith, who was outside the Capitol that day to protest about Donald Trump’s election defeat. “There was a group of grey-haired ladies – the average age had to have been mid-70s – that were praying.”

Nineteen months later, Smith is sitting in a cafe in his home city of Cheyenne in the western state of Wyoming. He condemns the violence that took place inside the Capitol but, despite a mountain of evidence, scoffs at the idea that Trump was responsible. And he is adamant that Cheney, his representative in Congress, should pay a price for her anti-Trump crusade.

The three-term congresswoman may lose her seat in Tuesday’s Republican primary election in Wyoming, the most watched congressional primary of the year. Opinion polls show Cheney trailing Harriet Hageman, conservative lawyer and vehicle of Trump’s vengeance, and defeat for the clarion voice of the January 6 panel will, in many eyes, make her a martyr for American democracy.

It will also signal a tectonic shift in Wyoming, the least populated state in America and one of the most devoutly Republican. Its most consequential political figure is Dick Cheney, vice-president under George W Bush and father of Liz. Last week, in cowboy hat, fleece and gruff tones, he recorded a campaign video for her, excoriating Trump as a “coward” and saying there has never been anyone who is a “greater threat to our republic”.

Victory for Hageman would therefore be widely interpreted as a repudiation of Wyoming’s most venerable political dynasty, evidence that the state Republican party no longer belongs to the Cheneys but to Trump. That would reflect a final national pivot away from the Bush era establishment to the “Make America Great Again” movement – from old school conservatism to far-right populism.

Smith, wearing a blue T-shirt that said “1776 Forever Free”, grey shorts and black flip-flops, is in no doubt which camp he belongs to. Last year he was a candidate in the Republican primary for Cheney’s House seat, raised $400,000 and made a pilgrimage to Trump’s golf club in Bedminster, New Jersey, to seek the former president’s all-important endorsement.

“It was like speed dating, my wife said,” the 48-year-old lawyer recalls. “I said, ‘I have a poll right here, sir, that shows that I could win today. Actually the polling that we took says that I could beat anybody in the state except for you, sir.’ He said, ‘Let me see that poll!’”

The pitch was unsuccessful and Trump gave Hageman the nod instead; Smith abandoned his campaign within a day and insists that he is not bitter. He is “100% behind Harriet Hageman” and shares her doubts – repeatedly debunked – about the legitimacy of the 2020 presidential election. “Liz Cheney, in our minds, betrayed the constitution, betrayed the nation, and we’re going to send her packing.”

Smith argues that Cheney – one of 10 House Republicans who voted to impeach Trump for inciting an insurrection – is bitter about Trump’s criticism of her father as the mastermind of a neoconservatism that led to the torturing of suspects, opening of a prison at Guantánamo Bay and waging of an illegal war on Iraq.

“It was a vendetta. She’s mad at Trump because Trump pointed out the truth of the Cheney foreign policy. Her dad is responsible for millions of deaths worldwide and trillions of dollars in spending from the US government. She’s pissed about it and she’s a narcissist and she saw her opportunity to go for Trump’s throat and she did.

“But it’s bigger than that. She wants to be the first woman president. We all know that. We’re not stupid. She’s going to ‘educate’ us in the constitution and how ‘we’re wrong and she’s right.’ Well, she’s got news and she’s got something coming for her on Tuesday of next week. She’s gonna find out if she educated us or not.”

The accusation that Cheney, 56, is driven by personal ambition in Washington, rather than by the needs of her constituents in Wyoming, is common among her critics here.

They complain that she has devoted more time to the televised hearings of the January 6 committee, where she serves as vice-chair, than to retail politics in her home state. Her campaign ads emphasise her role on the national stage as a defender of the constitution.

James King, a political science professor at the University of Wyoming, said Cheney’s opponent has seized on the theme that “she is too much Washington and not enough Wyoming”.

He added: “Certainly her participation in the committee and its public hearings have done nothing to change that view; if anything, it would be reinforcing it. It’s not just a support or not support Trump; it’s also, they will argue, too much the national and not enough the state: ‘She’s not of Wyoming any longer.’ It’s easy to say this is about Donald Trump but from the state angle it’s: ‘You’re not paying attention to us.’”

Indeed, Cheney has raised more than $13m largely thanks to donations from outside Wyoming, a vast sum for a congressional primary and far ahead of Hageman, who has travelled the state extensively to court voters. This, too, is seen as evidence that the incumbent is beholden to outside interests.

In Cheyenne, the state capital, Dianna Burchett, 62, a nurse who has voted for Cheney in the past, said: “She was put in office to do what the people of Wyoming wanted her to do and she went against the people of the state. She needs to keep her views to herself but she’s on a witch-hunt or blood hunt. It’s inexcusable.”

Laura Harnish, 53, an administrator who used to sit on an election committee for Dick Cheney, added: “I wouldn’t vote for Liz Cheney if she was the last person on the ballot. The January 6 committee was very badly done. She wasn’t representing Wyoming at that point. I vote for you. That’s who you represent: Wyoming. If you’re not going to do that then you don’t need to be in office. You need to find something else to do.”

In Wyoming, home to just 581,348 people, voters expect a certain level of intimacy with politicians. Mike Sullivan, the state’s former governor, described it as “a small town with unusually long streets”, and locals say that anyone who suffers a flat tyre never has to wait long for a helping hand.

In Cheyenne, the “Magic City of the Plains”, members of the public can wander freely about the state capitol building with a lack of security restrictions that evokes an earlier time. The house of representatives chamber nods to the state’s origins with paintings representing “cattlemen”, “homesteaders”, “stage coach” and “trappers”.

Wyoming has long had a way-out-west independent streak: in 1869 it became the first territory or state to grant women the right to vote and, in 1925, elected America’s first female governor, Nellie Tayloe Ross. Known as both the “Equality State” and “Cowboy State”, in the 1990s it welcomed visitors with signs that proclaimed: “Like no place on earth.”

Even today it can feel remote from national trends. It has no major professional sports team and, since 1983, no scheduled passenger rail service. The state museum in Cheyenne notes that “for centuries, Wyoming was a place to journey through rather than a destination … the ‘Highway of the West’.”

But in 2020 this was the state where Trump scored his biggest margin of victory, 43 percentage points. In downtown Cheyenne, the Republican party office window displays a prominent sign: “Election integrity”. Inside, in uneasy coexistence, the wall features portraits of former presidents Abraham Lincoln, Ronald Reagan and Trump as well as a commemorative photo of Bush and Cheney’s inauguration in 2001.

Loyalty to the Cheneys still runs deep in some quarters. On Tuesday afternoon, Richard Gage, 67, a lawyer, was hosing bushes outside his office. The lifelong Republican reflected: “She’s done a great job and she’s one of the few people with the courage to stand up to Donald Trump. He’s trying to destroy my democracy. He’s trying to overturn an election that he lost and that’s a direct threat to democracy itself.”

Gage has a Cheney sign displayed prominently and said it has resulted in rubbish being thrown on his lawn, a glimpse of how this campaign has taken on a menacing tone. Cheney herself has faced death threats and been forced to abandon traditional campaign stops and public rallies in favour of small-scale private events.

Joseph McGinley, a Republican county state committeeman who praises Cheney for “leadership in action” and believes she “would make a great president”, said: “There have been people that are supporting Hageman that have been stealing Cheney signs and vandalising Cheney signs.

“I was away for the weekend and came back and half the Cheney signs were gone, even in our neighbourhood, not in a very public area. The stealing of Cheney signs is a real thing and that’s unfortunate. It shows the people that are supporting Hageman are willing to do anything and they’re afraid Cheney is going to win.”

McGinley, 47, a doctor and entrepreneur based in Casper, said the battle for the soul of the state party can be traced back to the conservative Tea Party movement during the Barack Obama era. “They truly put in a ground game and it was many years and, if you were in the party, you could actually see it occurring.”

This made for a party shifting under the Cheneys’ feet. Dick is deep in retirement but Liz has effectively been excommunicated by the state party, which voted last year to censure her before deciding to stop recognising her as a Republican altogether. Local party offices offer yard signs for Hageman and many other Republicans on the ballot but not Cheney.

The congresswoman has therefore turned to an unlikely group for help: Democrats. Her campaign website features a link to a form allowing voters to change their party affiliation to Republican to take part in the Republican primary. This unusual move is based on an appeal to pragmatism in what is effectively a one-party state; Wyoming has voted Republican in every presidential election since 1968.

It appears to be working. In January, according to the secretary of state’s office, there were 196,179 registered Republicans in the state and 45,822 registered Democrats. As of 1 August, this had shifted to 207,674 registered Republicans and 39,753 registered Democrats.

David Martin, communications director of the Wyoming Democratic party, said: “I know a few people personally who have already switched over. I don’t think I’ll ever forget what one of them told me and she put it bluntly: ‘I’m voting to keep the crazies out.’”

No “crossover” voter is more prominent than Sullivan, the former governor, who after six decades as a registered Democrat recently switched to Republican so he could vote for Cheney. The 82-year-old retired lawyer explained by phone from Casper: “There are times when politics takes a backseat. Her work has been extraordinary and it’s reflective of both her intellect and her leadership.”

Sullivan, who served as governor from 1987 to 1995, said he was aware of Cheney yard signs being defaced or torn down in his neighborhood. “The nature of Liz’s opposition is more mean-spirited than when I was in office. You can attribute that to a lot of things but certainly President Trump opened the door to make that more mainstream than it has otherwise been.”

Cheney has not ruled out a 2024 presidential run as a Republican or an independent. Asked if he would consider supporting her, Sullivan replied: “I’d have to make that decision at the time. Now, whether I can picture her running for president under the circumstances in which she finds herself, I don’t know. I’m convinced she’s going to come out with a very powerful legacy: the profile in courage sort of legacy that is going to put her in good stead.”

Like her father, who under President Gerald Ford was the youngest chief of staff in White House history, Cheney plays a decades-long game. At one of the January 6 hearings, she reminded fellow Republicans that there will come a day when Trump is gone. Defeat on Tuesday might be the end of one career but the launchpad for another with even greater ambitions.

Not all Democrats, however, are ready to embrace a conservative who used to appear regularly on Rupert Murdoch’s Fox News and, according to the FiveThirtyEight website, voted in line with Trump’s position 93% of the time during his presidency.

Ted Hanlon, 63, running a long-shot campaign for the state senate, said: “I’ve been in Wyoming all my life. I knew her and I knew her dad and I have no evidence yet that a Cheney did something that was not self-serving.

“I’m glad she’s doing the January 6 hearings. If any other Republicans had been on the January 6 committee it would not have gone as well as it has and would not have come as close to the truth as it has. So I’m grateful that she’s there. It does not cause me to admire her in any way though.”