Trump endorses Harriet Hageman in her effort to unseat Rep. Liz Cheney

Former President Donald Trump has endorsed Harriet Hageman, a primary challenger to incumbent Rep. Liz Cheney, R-Wyo., ahead of Hageman’s Thursday afternoon announcement that she will run for Cheney's seat in the House of Representatives.

His endorsement both strikes back at Cheney, who voted for Trump’s impeachment in January and is serving on the Jan. 6 House select commitee, and is another test of how much weight his backing carries in primary races.

"Unlike RINO [Republican in name only] Liz Cheney, Harriet is all in for America First. Harriet has my Complete and Total Endorsement in replacing the Democrats number one provider of sound bites, Liz Cheney. Make America Great Again!" Trump said in a statement on Thursday morning through his Save America political action committee.

Trump also said that Hageman "is strong on Crime and Borders, powerfully supports the Second Amendment, loves our Military and our Vets, and will fight for Election Integrity and Energy Independence."

POLITICO reported last month that that Trump and Hageman, who ran for governor in 2018, were going to meet to discuss a congressional bid.

Hageman, an attorney and former national committeewoman for Wyoming on the Republican National Committee, supported Cheney in previous campaigns. But in a statement on her campaign website, she said Cheney had lost her support.

"Like many Wyomingites, I supported Liz Cheney when she ran for Congress. But then she betrayed Wyoming, she betrayed this country, and she betrayed me," Hageman said. "Every time Wyomingites see President Biden fail us and harm the interests of our nation and our state, they have Liz Cheney to thank."

Cheney fired back at Trump’s endorsement on Twitter, posting a picture of Trump’s statement with "number one provider of sound bites, Liz Cheney" highlighted in yellow.

"Here’s a sound bite for you: Bring it," Cheney wrote.

"I am honored to represent the people of Wyoming and proud of my strong conservative record," Cheney said in a statement to ABC News.

"It is tragic that some in this race have sacrificed those principles, and their duty to the people of Wyoming, out of fear and in favor of loyalty to a former president who deliberately misled the American people about the 2020 election, provoked an attack on the U.S. Capitol, and failed to perform his duties as president as the violence ensued."

The upcoming Republican primary in Wyoming, which only has one congressional district, will pit Cheney against multiple primary challengers.

Wyofile, a Wyoming-based news service, reported on Wednesday that voters in the state have been receiving illegal robocalls asking about Cheney's primary challengers. The Wyoming Republican Party has said the calls "are not being generated on behalf of any Wyoming Republican state or county party."

ABC News’ Meg Cunningham and John Parkinson contributed reporting.