WASHINGTON >> Rep. Liz Cheney has been thinking lately about her great-great-grandfather, a man who fought for the Union in the Civil War, as the House committee investigating the Jan. 6, 2021, U.S. Capitol insurrection prepares to launch a prime-time hearing of its work.

The Wyoming congresswoman, a member of one of America’s famous political families, is one of just two Republicans on the 1/6 panel, and its vice chair. Cheney helped drive the committee’s investigation into Donald Trump’s relentless efforts to overturn the 2020 presidential election, and has become one of the former president’s fiercest critics after a mob of his supporters laid siege to the Capitol to try to stop Congress from certifying Joe Biden’s victory.

Thursday’s televised hearing could be a pivotal moment in her political legacy — elevating her ambitions as a post-Trump party leader or possibly costing Cheney her job.

“I have found myself, especially since January 6th, thinking often of my great-great-grandfather and of the Union he fought to defend,” Cheney said in a recent speech.

“The question for every one of us is, in this time of testing, will we do our duty?” she asked after receiving a 2022 Profile In Courage Award from the John F. Kennedy Library Foundation in Boston. “Or will we look away from danger, ignore the threat, embrace the lies?”

Cheney has not shied from tough battles since she was elected to the House in 2016, alongside Trump’s own election, a staunch conservative whose family settled in Wyoming generations ago and who easily won the Republican-heavy Western state’s lone congressional seat.

In one of her first news conferences with party leaders, the daughter of former Vice President Dick Cheney unabashedly backed the enhanced interrogation techniques he helped champion in the post-9/11 era. Many others in Washington had said it was time to end the practice, regarding it as torture.

Known as an inside player with a famous family name, she is now thrust onto a national stage at a critical moment. Her singular mission to stop Trump from ever being president again after he spread false claims of voter fraud that spurred the attack on the Capitol may be among her last in Congress.

Barbara Comstock, a former Republican congresswoman in Virginia, said Cheney grew up steeped in principles and the belief that “this is why you’re in public service, to do the right thing.”

Comstock compared Cheney to Republican Margaret Chase Smith, the U.S. senator from Maine who stood up to Sen. Joseph McCarthy and the GOP over unproven allegations and smears against Americans whose lives were upended after being labeled as communists.

“History does have a way of sorting this out, and I think Liz understands that,” Comstock said.

Booted by Republicans from her No. 3 position in House GOP leadership for joining the 1/6 committee, Cheney now faces the full force of the Trump wing of the Republican Party apparatus trying to remove her from office by supporting a primary opponent. Wyoming tilts strongly Republican, almost guaranteeing the winner of the party’s August primary will win the general election in November.

Trump is campaigning against Cheney, as he has gone after the 10 House Republicans who joined Democrats in voting to impeach him over the insurrection — the only president to be twice impeached.

The former president recently arrived in Wyoming, filling the Casper event center to rally in support of Harriet Hageman, the fiery attorney and state party leader challenging Cheney.

“The people of Wyoming are going to vote dump this woman, Liz Cheney,” Trump predicted.

As Trump ran through a list of grievances about those disloyal to him, he said that worse than his Democratic political opponents are “the backstabbing RINO Republicans” — an acronym for “Republicans in Name Only” — and cited Cheney as among them.

Other Republicans have followed Trump’s lead. House GOP leader Kevin McCarthy, who is laboring to stay close to Trump as Republicans try to wrest control of the House from Democrats in the midterm elections, has shunned the congressional tradition of backing incumbent colleagues and instead endorsed Hageman and sent campaign cash her way.

“You have a congresswoman who’s obsessed with attacking President Donald J. Trump,” said McCarthy, who hopes to become the next House speaker, in a video address to the rally crowd.

James King, a political science professor at the University of Wyoming, said has he has never seen a serious challenge to an incumbent member of Congress in the state in his 30 years observing local politics.

“It’s an unusual situation, but then the last year and a half has been an unusual situation,” King said.

He said he’s not sure the televised Jan. 6 hearings will hurt or help Cheney’s standing back home.

“I think most people will have made up their mind — they have either decided that Cheney is a traitor to what they voted for in 2020, or they are behind Cheney in searching for the truth behind the Jan. 6 events,” he said.

Still, other notable Republicans, including Senate Republican leader Mitch McConnell, have quietly supported Cheney’s campaign.

Strategists see a path for Cheney’s reelection by drawing a coalition of moderate Republicans and crossover Democrats who are eligible to vote in the GOP primary after the state government bucked Trump’s push to tighten the rules.

The Republican Party in Wyoming has become more extreme, and its chairman, Frank Eathorne, was spotted in images of those outside the Capitol during the riot.

“We’re fed up with Liz Cheney,” Hageman said at the rally.

After the long assault on the Capitol on Jan. 6, Congress reconvened that night to pick up where it had left off — certifying the election results submitted by the states.

Cheney said she walked through the building, into Statuary Hall, the historic space filled with law enforcement officers in tactical gear “sitting on the floor, leaning up against the statues, exhausted from the brutal hand-to-hand combat in which they had been engaged for hours.”

She made her way to the next room, the Capitol Rotunda, “watched over by statues of Washington and Jefferson, and Lincoln and Grant, and Eisenhower, and Ford and Reagan.”

Its giant paintings, she noted, included one that depicts George Washington resigning his military commission after the Revolutionary War — voluntarily relinquishing his command in a stunning act that set the stage for the future presidential tradition.

“And this sacred obligation to defend the peaceful transfer of power has been honored by every American president — except one,” she said.

Thinking about her great-great-grandfather Samuel Fletcher Cheney, she said it’s time for this generation to “set aside partisan battles and stand together to perpetuate and preserve our great republic.”