Republican Liz Cheney has campaigned with Democratic presidential candidate Kamala Harris and urged voters in the United States to reject the “depraved cruelty” of her rival, former President Donald Trump.

“I’ve never voted for a Democrat, but this year I’m proudly casting my vote for Vice President Kamala Harris,” Cheney said on Thursday, at an event in the swing state of Wisconsin.

“Putting patriotism ahead of partisanship is not an aspiration. It is our duty.”

Her appearance with Harris took place in the small community of Ripon, where, in 1854, the Republican Party was established.

When Harris spoke afterwards, she thanked Cheney and said she stood in the “finest tradition” of the Republican Party’s leaders.

“She possesses some of the qualities of character I most respect in any individual and any leader – courage, especially at a moment like this,” said Harris. “When there are so many powerful forces intent on trying to demean and belittle and make people afraid.”

Vice President Kamala Harris, left, shakes hands with former Congresswoman Liz Cheney in Ripon, Wisconsin [Mark Schiefelbein/AP Photo]

Ex-vice president also backs Democrat

The appearance of Cheney, 58, and Harris, 59, came a month after the one-time Wyoming congresswoman said she and her father, former Vice President Dick Cheney, would be supporting Harris over Trump.

“As a conservative, as someone who believes in and cares about the Constitution, I have thought deeply about this, and because of the danger that Donald Trump poses, not only am I not voting for Donald Trump, but I will be voting for Kamala Harris,” she said in remarks on September 4.

On Thursday, Cheney repeated her concerns about Trump, the de facto leader of the Republican Party, while delivering a full-throated endorsement of Harris.

“Vice President Harris has dedicated her life to public service. I know she loves our country, and I know she will be a president for all Americans. As a conservative, as a patriot, as a mother, as someone who reveres our Constitution, I am honoured to join her in this urgent cause,” she said.

Cheney also explicitly referenced Trump’s attempts to sow doubt in the integrity of US elections.

In the wake of the 2020 presidential race, Trump refused to accept his defeat to Democrat Joe Biden, instead alleging widespread voter fraud “rigged” the results — a false claim.

“As we meet here today, our republic faces a threat unlike any we have faced before: a former president who attempted to stay in power by unravelling the foundations of our Republic by refusing to accept the lawful results, confirmed by dozens of courts, of the 2020 election,” Cheney said.

Former Vice President Dick Cheney, Liz Cheney’s father, has also indicated would back Harris in the 2024 presidential race [Patrick T Fallon /AFP]

‘Reject the depraved cruelty’

Cheney’s visit to Wisconsin came a day after a federal judge unsealed a 165-page court filing outlining new evidence against Trump in a case accusing him of election interference in 2020.

Trump has pleaded not guilty to four federal charges of conspiracy and obstruction.

As she spoke to voters on Thursday, Cheney denounced Trump’s character as unpresidential. “I ask you to meet this moment. I ask you to stand in truth, to reject the depraved cruelty of Donald Trump, and I ask you instead to help us elect Kamala Harris for president.”

During her congressional career, from 2017 to 2023, Cheney rose to be the third-most senior Republican in the House of Representatives until she angered Trump and was forced out of her leadership role.

Cheney was one of 10 Republican members of Congress who voted to impeach Trump in 2021.

The move came days after thousands of Trump supporters stormed the US Capitol on January 6, 2021, as part of an alleged effort to prevent the certification of Biden’s victory.

She was also the top Republican on the House committee that investigated the January 6 insurrection. Trump vowed revenge on those who had spoken against him, and in the summer of 2022, Cheney lost her primary in Wyoming to a challenger who had Trump’s support.

There was no immediate response from Trump to Thursday’s rally.

Wisconsin is one of a handful of battleground states that have previously been won by just a few thousand votes.

A poll by The New York Times currently gives Harris a two-point lead in the state.