Liz Cheney, a congresswoman representing the US state of Wyoming, publicly rebuked former president Donald Trump on Monday for claiming the 2020 election was "fraudulent" and accused him of “poisoning our democratic system".
Ms Cheney, the third most powerful Republican in the House of Representatives and the daughter of former vice president Dick Cheney, took to Twitter to accuse Mr Trump – without mentioning him by name – of promoting lies.
"The 2020 presidential election was not stolen," Ms Cheney tweeted. "Anyone who claims it was is spreading THE BIG LIE, turning their back on the rule of law and poisoning our democratic system."
Her remarks came less than two hours after Mr Trump issued a statement proclaiming that the 2020 presidential election “will be, from this day forth, known as THE BIG LIE!”
Mr Trump has refused to concede his loss to President Joe Biden despite Congress certifying the election results in January and the courts dismissing his lawsuits on the subject due to lack of evidence.
Since then, an intraparty feud has developed in the Republican ranks, with Ms Cheney and Mitt Romney, a former presidential candidate and senator from Utah, becoming the most vocal of Mr Trump's critics. They were among the 10 Republicans who voted to impeach Mr Trump following the deadly riots at the Capitol on January 6.
But they have faced backlash within the Republican Party, with members calling for Ms Cheney's removal in February as the party's conference chair. She eventually prevailed in that vote 145-61, however she has recently become the target of Trump loyalists once again.
"This idea that you just disregard president Trump is not where we are, and, frankly, he has a lot to offer still,” Steve Scalise, the House minority whip, told Axios last week.
Ms Cheney is up for re-election in 2022 and she is already facing challengers from the Trump camp in her home district.
But moderate voices within the party are defending its diversity of views.
"We need to have room for a variety of views. We are not a party that is led by just one person,” Susan Collins, a senator from Maine, told CNN on Sunday.