Donald Trump announced Thursday that he is endorsing Harriet Hageman to take on Republican Rep. Liz Cheney in a Wyoming primary contest that will serve as the marquee test of the former president's ability to purge his critics from the party, particularly lawmakers who challenge his false claims about the 2020 presidential election. 

Trump has vowed to unseat Cheney since she voted to impeach him in January over his role in the Jan. 6 attack on the Capitol, which was carried out by a mob of supporters who echoed Trump's false claims about the election while seeking to stop Congress from certifying its results and declaring Joe Biden the president-elect.

In a statement, Trump called Cheney a "warmonger and a disloyal Republican," said Sen. Cynthia Lummis, R-Wyo., who also backs Hageman over Cheney.

"Unlike RINO Liz Cheney, Harriet is all in for America First," Trump said, adding that she has his endorsement in "replacing the Democrats number one provider of sound bites, Liz Cheney."

In a quick response, Cheney tweeted, "Here's a sound bite for you: Bring it."

Hageman this week stepped down as the state's national Republican committeewoman in advance of Trump's announcement and is a lawyer who has worked on cases challenging federal actions on water rights and natural resources. She ran unsuccessfully for governor in 2018, finishing third in a six-person primary that was won by Gov. Mark Gordon.

Hageman has previously supported Cheney, donating to past campaigns and serving as an adviser to her failed Senate bid in 2013. But like many Republicans, she has turned on the Wyoming lawmaker because of Cheney's outspoken criticism of Trump.

The news of Trump's decision to endorse Hageman was first reported by Politico.

Trump has also endorsed primary challengers against some of the other nine House Republicans who voted to impeach him. In recent days, he announced his endorsement of Michigan state lawmaker Steve Carra to face off against Rep. Fred Upton (Mich.), who has served in Congress for almost 35 years, and Joe Kent to challenge Rep. Jaime Herrera Beutler (Wash.). Earlier this year, Trump endorsed former campaign and White House aide Max Miller in a primary contest against Rep. Anthony Gonzalez (Ohio), holding a rally in June to highlight his desire to unseat the congressman over his impeachment vote.

But Cheney has been his prime target due to her high profile and role as an avatar of the more militarily hawkish and business-friendly Republicans that led the party before his brand of nativism and populism propelled him to the presidency. Cheney is the daughter of former Vice President Richard B. Cheney and also served in the George W. Bush administration.

Cheney was kicked out of her House Republican leadership post in May due to her warnings that Trump's falsehoods about the election were a threat to democracy.

Many of her colleagues, including House Minority Leader Kevin McCarthy, R-Calif., said Cheney's criticism of Trump made her unsuitable for the No. 3 spot in leadership because she was "off message" and should be focusing on attacking the Biden administration, not the former president. But Trump continues to bring up his election loss rather than focus on the future and has received no similar criticism from GOP leaders.

Cheney was replaced in her leadership position by Rep. Elise Stefanik, R-N.Y., who frequently praises Trump and has called him the leader of the party.

Cheney has said her main goal is to make sure Trump's grip on the party slips and that he never holds the presidency again. After she was removed from her leadership post, she did a series of interviews with national news organizations in which she made the case that Trump is unfit to be a party leader and called out GOP colleagues who continue to be loyal to him.

"I intend to be the leader, one of the leaders, in a fight to help to restore our party, in a fight to bring our party back to substance and principles, and in a fight to make clear that we won't participate in the really dangerous effort that's underway," Cheney said in a May 12 interview with NBC's "Today" show.

She called her ouster from leadership an "opening salvo" in a "battle we have to win, because it's not just about the Republican Party, it's about the country."

Cheney is one of two Republicans serving on a select committee created to investigate the Jan. 6 attack on the Capitol. The panel recently sent out a series of requests for information to federal agencies as well as social media and telecommunication companies pertaining to the attack on the Capitol and Trump's efforts to subvert the election.

Trump blasted the committee last month when it sought information from his time in the White House.

"The Leftist 'select committee' has further exposed itself as a partisan sham and waste of taxpayer dollars with a request that's timed to distract Americans from historic and global catastrophes brought on by the failures of Joe Biden and the Democrats," he said in a statement.