(Bloomberg) -- Former President Donald Trump ripped into Republican US Representative Liz Cheney at a rally in Wyoming Saturday, as part of his quest to defeat the incumbent who has emerged as his most vocal and active GOP critic.

“Few members of Congress in history have personally caused more damage and destruction to our Republican Party” than Cheney, he said. “She’s aided and abetted the radical Democrat Party in one of the most unhinged, lawless and dangerous witch hunts of all time,” referring to the House committee investigating the Jan. 6, 2021, insurrection at the US Capitol.

The rally was held in Casper, Wyoming, in support of Harriet Hageman, whom Trump has endorsed in the Aug. 16 GOP primary for the state’s lone congressional seat. Throughout his speech Trump repeatedly referred to Cheney, the daughter of former Vice President Dick Cheney, as a “Republican In Name Only,” or RINO.

“In many ways, worse than the terrible Democrats, are the backstabbing RINO Republicans who are helping them do their act,” Trump said. “There is no RINO in America who has thrown in her lot with the radical left more than Liz Cheney.”

Trump has targeted Cheney since she was one of 10 House Republicans who voted to impeach him for his role in the insurrection, when Trump supporters stormed the Capitol to stop the counting of Electoral College votes for Joe Biden. 

She further incurred the former president’s wrath by accusing him of threatening democracy with false claims that the 2020 election was stolen and serving as vice chair of the House committee investigating the insurrection.

Cheney officially filed for re-election on Thursday, saying in a video posted online that she’s asking for support because the Wyoming election matters and “this is a fight we must win.”

“If our generation does not stand for truth, the rule of law, and our constitution, if we set aside our founding principles for the politics of the moment, the miracle of our constitutional republic will slip away,” she said. “We must not let that happen.”

Cheney’s opposition to Trump led to her ouster last year from GOP House leadership. Both House Minority Leader Kevin McCarthy and New York Representative Elise Stefanik, who replaced Cheney as the No. 3 GOP House leader, are scheduled to make video appearances at the rally.

Besides campaigning for Hageman, Trump’s Save America political action committee has given $500,000 to a political action committee running television ads in Wyoming against Cheney featuring his oldest son, Donald Trump Jr.

Hageman, a Wyoming attorney who ran unsuccessfully in the GOP primary for Wyoming governor in 2018, had previously been a supporter of Cheney’s.

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