Republican Rep. Liz Cheney, co-leader of the House Jan. 6 committee and a staunch critic of former President Donald Trump, is endorsing Democratic Rep. Elissa Slotkin in her tough reelection fight in Michigan.
The move, which a member of Cheney's staff confirmed to CNBC, is the Wyoming Republican's first-ever endorsement of a Democrat. It's also Cheney's first endorsement since Trump-backed GOP challenger Harriet Hageman trounced the incumbent in the Wyoming primary.
Cheney and Slotkin are set to campaign together in Lansing on Tuesday, the Democrat's campaign said.
Cheney has denounced Trump, his political allies and apologists in the Republican Party since Jan. 6, 2021, when a violent mob of the then-president's supporters stormed the U.S. Capitol.
Cheney's colleagues censured her and stripped her of her leadership role for her criticism of Trump, who remains the de facto leader of the GOP. She is the vice chair of the House select committee investigating the insurrection and one of two Republican members of the panel.
Slotkin, a two-term congresswoman, is fighting to keep her seat in Michigan's newly drawn 7th Congressional District, where she faces a major threat from Republican State Sen. Tom Barrett. Cook Political Report rates the race a toss-up.
A source close to Cheney told CNBC that Barrett is "an election denier" who refuses to acknowledge Trump's loss to President Joe Biden in the 2020 vote. Barrett joined 10 other state senators in signing a 2021 letter asking Congress to investigate unfounded voter fraud claims, Michigan Advance reported.
Trump's false claims about a "rigged" election fueled many of his supporters to storm the Capitol. Polls have shown large numbers of Republicans still question Biden's electoral victory, and a majority of GOP nominees on the ballot for the midterms have reportedly cast doubt on the results.
"I'm proud to endorse Elissa Slotkin," Cheney said in a statement shared by the Democrat's campaign. "Serving together on the Armed Services Committee, I have come to know Elissa as a good and honorable public servant who works hard for the people she represents, wants what's best for the country, and is in this for the right reasons."
"While Elissa and I have our policy disagreements, at a time when our nation is facing threats at home and abroad, we need serious, responsible, substantive members like Elissa in Congress," Cheney said. "I encourage all voters in the 7th district — Republicans, Democrats, and Independents — to support her in this election."
Slotkin said in a statement that Cheney has been a critical voice "at a moment when the very heart of our democracy is being challenged."
"I'm grateful for her support in this race and I'm proud of the work we've done together to strengthen our national security and America's role in the world," Slotkin said.