Former Republican Congresswoman Liz Cheney has said she is backing Democratic presidential nominee Kamala Harris for president in the November election.

Cheney said on Wednesday she would vote for Harris “because of the danger that Donald Trump poses” as she cited her credentials as “a conservative, as someone who believes in and cares about the constitution”.

She became one of the fiercest critics of Republican contender Trump after his alleged inaction as president and for fanning the flames when thousands of his supporters stormed the US Capitol on January 6, 2021, in an effort to overturn his election defeat.

Cheney came out for Harris at an event at Duke University in North Carolina, according to a video of her comments, posted on social media platform X.

Once considered Republican royalty, the daughter of former Vice President Dick Cheney was ostracised by the party after co-chairing the congressional panel investigating the assault on the Capitol.

She paid the price by losing her seat in Congress to a Trump-backed challenger in her 2022 Republican primary in Wyoming.

Harris’s campaign chair Jen O’Malley Dillon said in a statement on Wednesday night: “The Vice President is proud to have earned Congresswoman Cheney’s vote. She is a patriot who loves this country and puts our democracy and our Constitution first.”

Cheney joins other Republicans, like fellow January 6 committee member Adam Kinzinger and Denver Riggleman, both former congressmen, in supporting Harris.

More than 200 alumni of the Bush administration and former Republican presidential campaigns of the late Senator John McCain and Senator Mitt Romney also announced their endorsement of Harris last week.

Asked for comment, Trump campaign spokesman Steven Cheung responded: “Who is Liz Cheney and what does she do?”