Former Wyoming Rep. Liz Cheney — a lifelong Republican, the daughter of former Vice President Dick Cheney, who served in the State Department under George W. Bush’s administration, three-term congresswoman and one-time Chair of the House Republican Conference — likely never thought she’d be standing on stage in support of a Democratic presidential candidate.

But that’s exactly what she did in Wisconsin on Thursday, declaring to a crowd gathered at Ripon College in Ripon, Wisconsin — the birthplace of the Republican Party — that she will be voting for Kamala Harris in November.

“I have never voted for a Democrat, but this year, I am proudly casting my vote for Vice President Kamala Harris,” Cheney said, to cheers of “Thank you, Liz” from the crowd.

“Thank you,” she replied, before echoing one of Harris’ signature campaign slogans. “But mostly, we’re not going back.”

Cheney, who became one of the most prominent Republican critics of Donald Trump following the Jan. 6, 2021, riot at the U.S. Capitol, said that the country “faces a threat unlike any we have faced before: a former president who attempted to stay in power by unraveling the foundations of our republic by refusing to accept the lawful results, confirmed by dozens of courts, of the 2020 election.”

“We cannot turn away from this truth,” she said. “In this election, putting patriotism over partisanship is not an aspiration. It is our duty.”

Cheney, one of two Republican party members who worked on the House committee that investigated the Jan. 6, 2021, storming of the U.S. Capitol, lost both her leadership role in the House GOP conference and her seat in Congress for her opposition to Trump. Despite her ouster from Congress in the state's Republican primary two years ago, she has still continued to criticize Trump, and endorsed Harris last month. Her father, one of the most prominent conservatives of his generation, has done the same. 

“At the very heart of our survival as a republic is the peaceful transfer of power,” Cheney continued, before invoking someone who often isn’t mentioned at Democratic election rallies, Ronald Reagan, who once called America’s tradition of a bloodless handoff between administrations “nothing short of a miracle.”

“In the United States of America, violence does not, and must never, determine who rules us. Voters do,” she declared. “And in this country, under our Constitution, our president has a particular solemn obligation to ensure and guarantee the peaceful transfer of power. Since the beginning of the republic, every president in our history has fulfilled that duty, every president until Donald Trump.”

Cheney ran through some of the accusations laid out in special counsel Jack Smith’s bombshell filing in the federal election subversion case against Trump, calling his actions on Jan. 6 “depravity” and branding him “petty,” “vindictive, “cruel” and “not fit to lead this good and great nation.”

"He praised the rioters," she said. "He did not condemn them. That’s who Donald Trump is."

But Harris, Cheney said — while far apart on certain issues — is someone who is “standing in the breach at a critical moment in our nation's history” and is “working to unite reasonable people from all across the political spectrum.”

“I know that a President Harris will be able to unite this nation,” she said. "I know that she will be a president who will defend the rule of law, and I know that she will be a president who can inspire all of our children, and if I might say so, especially our little girls.”

Harris called it a “profound honor” to have Cheney’s support, and also offered her thanks to her father, Dick Cheney, for his backing. “We may not see eye-to-eye on every issue, and we’re going to get back to a healthy two-party system, I’m sure of it.”

"In the face of those who would endanger our magnificent experiment, people of every party must stand together,” Harris declared.

"The tragic truth that we are facing in this election for president of the United States is that there is actually an honest question about whether one of the candidates will uphold the oath to the Constitution of the United States," the vice president said, flanked by signs reading "Country Over Party."

Harris was also endorsed Thursday by former Trump White House staffer Cassidy Hutchinson, who was a key witness during the House Jan. 6 committee's investigation.

"I am really, really proud as a conservative to have the opportunity to vote for Kamala Harris and Tim Walz in this election," Hutchinson, a former aide to White House Chief of Staff Mark Meadows, said during an MSNBC interview with Lawrence O'Donnell on Wednesday.

Hutchinson said she values policy and, while she acknowledged there are few issues she and Harris agree upon, "I hope that we would be able to come to consensus on a lot more issues, but in saying that, the character of our leaders really matters, too."

Donald Trump and JD Vance cannot be trusted with the Constitution or to uphold the rule of law, she said, adding, "That in and of itself is disqualifying."

In her endorsement, Hutchinson spoke directly to GOP voters, saying, "I understand how frightening it can be to potentially break with your party. I also understand there are very valid concerns about inflation."

Still, she said, Trump and Vance could not be trusted "to enact responsible policy."

In addition to casting her ballot for Harris, Hutchinson said she intends to vote for Democratic Senate and House candidates "because I think it's important that we get past this period of Donald Trump for America to begin healing."

Ripon, a town of 7,863 in central Wisconsin, is the site of a one-room schoolhouse where meetings took place that eventually helped form the Republican Party in 1854. The schoolhouse is now a National Historic Landmark.

Harris has received the backing of more than 200 Republicans affiliated with former President George W. Bush, the late Arizona Sen. John McCain and current Utah Sen. Mitt Romney. She is also backed by at least 100 GOP national security officials, including former 4-Star General Larry Ellis.

Spectrum News' Ryan Chatelain and Susan Carpenter contributed to this report.