Republican Liz Cheney looks set to lose her seat in the US Congress to an election conspiracy theorist, in the latest sign of her party's break with traditional conservatism to embrace Donald Trump's hardline "America First" agenda.

Once considered Republican royalty, the lawmaker from Wyoming has become a pariah in the party over her role on the congressional panel investigating the 6 January assault on the US Capitol - and Mr Trump's role in fanning the flames.

All eyes are on the primary in Wyoming, where defeat for the 56-year-old elder daughter of former vice president Dick Cheney would mark the end of the family's four-decade political association with one of America's most conservative states.

Even her loyal backers have privately accepted that Ms Cheney will likely lose the Republican nomination for November's midterms to 59-year-old lawyer Harriet Hageman – Mr Trump's hand-picked candidate who has amplified his false claims of a "rigged" 2020 election.

The latest survey from the local Casper Star-Tribune has Ms Cheney with just 30% support compared with 52% for Ms Hageman, reflecting all recent polling.

Yet there is already speculation that Ms Cheney may challenge Mr Trump for the Republican presidential nomination in 2024 - or even run as an independent - and insiders are expecting her to deliver a concession speech that will double up as the launchpad for her political future.

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'We will win'

"No matter how long we must fight, this is a battle we will win," she said in a video message posted before the weekend.

"Millions of Americans across our nation - Republicans, Democrats, independents - stand united in the cause of freedom."

Ms Cheney has framed her campaign as a battle for the soul of a party she is trying to save from the anticonstitutional forces of Trumpism.

She is the last of ten Republicans in the House of Representatives who backed Mr Trump's second impeachment to face primary voters.

Four retired rather than seek reelection, three lost to Trump-backed opponents, and only two - California's David Valadao and Dan Newhouse of Washington state - have made it through to November's midterm elections.

Ms Cheney, a tax-cutting, gun-loving right-winger, voted in line with Mr Trump's positions 93% of the time when he was president but that has not blunted his retaliation for her role in the House committee probe.

Mr Trump has made Ms Cheney his bete noire, calling her "disloyal" and a "warmonger," prompting death threats that have forced her to travel with a police escort.

The former attorney has been made persona non grata by the Wyoming Republican Party, whose chairman himself participated in the protests on the day of the US Capitol assault.

Palin comeback bid

In her state - the first to grant women the right to vote, in 1869 - the congresswoman has been forced to run a kind of shadow campaign, with no rallies or public events.

She even avoided the traditional election day photo op today, eschewing media at her local polling station to instead cast her ballot in nearby Jackson.

There are also elections in Alaska, where 2008 Republican vice presidential candidate Sarah Palin's comeback battle - to complete the term of a congressman who died in office - is dividing locals.

Fourteen years after rising to international fame on the losing Republican presidential ticket headed by John McCain, Ms Palin remains popular among women as the "soccer mom" who pioneered the ultra-conservative "Tea Party" movement that paved the way for Trumpism.

But many voters blame her for abandoning her single term as governor halfway through, amid ethics complaints, and a recent poll showed her to be viewed unfavourably by 60% of Alaskans.