Washington (AFP) - Liz Cheney's dogged pursuit of Donald Trump over last year's riot at the US Capitol has cemented her status as the sole Republican to gamble her career as she breaks ranks with her party in the fight for US democracy.

The 55-year-old congresswoman from Wyoming, a daughter of former vice president Dick Cheney, was once seen as the tax-cutting, God-fearing, small-government apotheosis of American conservatism.

But her refusal to accept Trump's false claims of a stolen 2020 election set her on a collision course with the Trump-dominated modern Republican Party, which booted her out of the leadership and disowned her at home in the "Cowboy State."   

Cheney was one of just 10 Republicans in the House of Representatives to vote to impeach the former president for inciting the January 6, 2021 insurrection by his supporters.

"Tonight, I say this to my Republican colleagues who are defending the indefensible: There will come a day when Donald Trump is gone, but your dishonor will remain," she said Thursday in her role as the vice-chair of the House committee investigating Trump over the insurrection. 

Cheney and her colleagues on the panel maintain that the president and his inner circle were part of a criminal conspiracy to overturn his 2020 election defeat to Joe Biden that culminated in the violence of January 6, 2021.

"In our country, we don't swear an oath to an individual, or a political party," Cheney said. "We take our oath to defend the United States Constitution. And that oath must mean something."

'Evasion and deflection'

Critics of the Republican leadership argue that it is an oath that the party largely abandoned in its unswerving fealty to its wayward leader, and the populist "America First" sentiment that swept him to power.

A year and a half after being defeated by Biden, Trump retains an iron grip on the Republican Party, which in February adopted as part of its official policy platform the falsehood that the mayhem at the Capitol constituted "legitimate political discourse." 

"The parts of the conservative elite that still have some self-knowledge know Liz Cheney is right," conservative commentator Bill Kristol tweeted on Friday.

"But they can't take a stand against the new (Trumpist) establishment of which they desperately want to be a part. So it's all evasion and deflection."

Only one other Republican, Adam Kinzinger, has joined Cheney's rebellion -- but the stakes are lower for the Illinois congressman as he retires anyway in January.  

Both have been tarred as "RINOs" -- "Republicans in name only" -- by colleagues with far less conservative voting records.

Other Republican lawmakers have tried to walk a fine line between condemning Trump's role in whipping up the crowd that stormed the Capitol and staying in his good graces.

Not Cheney.

"The president of the United States summoned this mob, assembled the mob, and lit the flame of this attack," she said as she explained why Trump deserved blame for the insurrection -- reprising word-for-word a withering assessment she first deployed during Trump's second impeachment.    

Wyoming political royalty

Cheney, the elder of Dick Cheney's two daughters, comes from a family that is the equivalent of political royalty in staunchly conservative Wyoming.

From 1979 to 1989, her now 81-year-old father held the House seat that she now occupies.

Dick Cheney resigned from Congress to become defense secretary under president George H.W. Bush and went on to serve for eight years as vice president under president George W. Bush.

After graduating from University of Chicago law school, Liz Cheney worked for the International Finance Corporation and served in various State Department posts.

She made an abortive bid for a US Senate seat from Wyoming in 2014 before winning election to the House in 2016.

She easily won re-election in 2018 and 2020, defeating her Democratic opponents by more than 40 points each time.

But the self-described "proud rodeo mom" of five children may have a tougher time around when she faces re-election in November.

Republican candidates are already lining up to challenge Cheney in the party primaries -- and Harriet Hageman, who has the backing of Trump, appears to have built up a substantial lead.

Cheney, Hageman alleged in a statement on Friday, is doing "nothing to fight for the people who are suffering, instead playing a central role in the illegitimate January 6 committee designed to distract people from the miserable record of President Biden."