WASHINGTON — Liz Cheney’s resounding primary defeat Tuesday to Harriet Hageman marks the end of an era for the Republican Party as well as her own family legacy, the most high-profile political casualty yet as the party of Lincoln transforms into the party of Trump.

The fall of the three-term congresswoman, who has declared it her mission to ensure Donald Trump never returns to the Oval Office, was vividly foreshadowed earlier this year, on the first anniversary of the Jan. 6 attack on the Capitol.

As the House convened for a moment of silence, Cheney, who is leading the investigation into the insurrection as vice chair of the 1/6 committee, and her father, former Vice President Dick Cheney, stood almost alone on the Republican side of the House floor.

Democratic lawmakers streamed by to shake their hands. Republicans declined to join them.

“Liz Cheney represents the Republican Party as it used to be. ... All of that is gone now,” said Geoff Kabaservice, vice president of political studies at the center-right Niskanen Center.

What comes next for Liz Cheney is still to be determined.

“Now the real work begins,” she said in an election night concession speech in Wyoming, summoning the legacy of both Abraham Lincoln and his Civil War-era military and presidential successor Ulysses Grant in her campaign against Trump.

Cheney could very well announce her own run for the White House — unlikely to win a hostile Republican Party’s nomination but to at least give those opposed to Trump an alternative.

Overnight, she transferred leftover campaign funds into a new entity: “The Great Task.” That's a phrase from The Gettysburg Address.

“I will be doing whatever it takes to keep Donald Trump out of the Oval Office,” Cheney told NBC's “Today” show early Wednesday. Pressed, she said that running for president “is something I’m thinking about and I’ll make a decision in the coming months.”

Whether she runs or not, her belief that Trump poses a danger to democracy is a conviction that runs deep in her family.

But it's a view that has no home in today’s GOP.

Trump is purging the Republican Party, ridding it of dissenters like Cheney and others who dare to defy him, shifting the coast-to-coast GOP landscape and the makeup of Congress.

Of the 10 House Republicans including Cheney who voted to impeach Trump for inciting the Jan. 6, 2021 insurrection, at the Capitol, only two remain candidates for re-election. The others have bowed out or, like Cheney, have been defeated by Trump-backed challengers.

If Republicans gain control of the House and Senate in the November elections, the new Congress is destined to be remade in Trump’s image. However, his influence may in fact cut two ways, winning back the House for Republicans but costing the party the Senate if his candidates fail to generate the broader appeal needed for statewide elections.

“It’s just a party of Donald Trump’s fever dreams,” said Mark Salter, a former longtime Republican aide to the late Sen. John McCain.

“It’s just Donald Trump’s club.”

For 50 years, the Cheneys have had important influence in Washington, from the time Dick Cheney first ran for Congress — later being elected vice president — to the arrival of his daughter, elected in 2016 alongside Trump's White House victory.

Identified with the hawkish defense wing of the Republican Party, the Cheneys with the Presidents Bush represented a cornerstone of the GOP in the post-World War II era, when it thrived as a party of small government, low taxation and muscular foreign policy.

Liz Cheney never wavered, chosen by House GOP colleagues to the same position her father held, the No. 3 Republican in the House, its highest-ranking woman.

But the Jan. 6, 2021, attack on the Capitol changed all that.

Cheney was unequivocal, laying blame for the attack on the defeated president and his false claims of voter fraud and a rigged election.

Trump “summoned this mob, assembled the mob and lit the flame of this attack,” she said at the time, announcing her vote to impeach.

“There has never been a greater betrayal by a president of the United States of his office and his oath to the Constitution.”

House Republican leader Kevin McCarthy initially defended Cheney but quickly reversed as Republicans booted her from party leadership. When Democratic Speaker Nancy Pelosi named Cheney to the 1/6 panel, her exile was all but complete.

Trump gloated at Cheney’s GOP primary defeat Tuesday night, deriding her as “sanctimonious” and a “fool” for suggesting his claims of a rigged election were false.

Trump had swooped into the Cowboy State to rally for Harriet Hageman, who was once highly critical of him but beat Cheney by embracing the former president, backed by McCarthy and other party leaders.

Cheney’s defeat follows that of the last Bush in public office, Jeb's son George P. Bush, who was defeated in the Republican primary for Texas attorney general by Trump-backed Ken Paxton in May.

On Fox News, conservative author Charlie Kirk called Tuesday's election a “mass repudiation” of the Bush-Cheney-McCain era.

Rep. Elise Stefanik of New York, who replaced Cheney in House GOP leadership and endorsed Hageman, said in a statement she was glad to see Pelosi’s “puppet” defeated.

Former Sen. Alan Simpson of Wyoming who served in Congress alongside Dick Cheney and has known Liz Cheney since she was a child, says he can no longer recognize the party that he joined, casting his first presidential vote for Dwight Eisenhower.

“What’s happened to our party is a fear of Donald J. Trump," Simpson said.

Founded in the mid-19th century, the Republican Party's core conservative values have shifted in the Trump era into a strain of politics that is more inward focused on grievances at home and isolationism abroad.

Those running for Congress include many Republican incumbents who voted against certifying Joe Biden’s election, amplifying Trump’s relentless false claims of a rigged election and fueling the Jan. 6 insurrection at the Capitol.

And many of the new GOP candidates for Congress are also election deniers, according to a tally by Democrats.

“The House is — should be — the people’s House," said former Republican Rep. Carlos Curbelo of Florida. Instead, he said, "It’s controlled by Mr. Trump,”

Cheney walks alone many days at the Capitol, flanked by plain-clothes Capitol police who guard her amid an onslaught of violent threats.

Her mission of denying Trump a return to the presidency can be seen in her daily schedule, much of her time devoted to the 1/6 committee deepening and completing its work.

Fellow Wyoming Republican Simpson said he has no doubt what's next for Cheney: “She’ll mount a new set of horses and ride to the finish line.”