Alberto Gonzales, a Republican attorney general under the George W Bush administration, has announced his endorsement of Kamala Harris.
"As the United States approaches a critical election, I can't sit quietly as Donald Trump - perhaps the most serious threat to the rule of law in a generation - eyes a return to the White House," Gonzales, who served as the US's 80th attorney general from 2005 to 2007, wrote in an article for Politico.
"For that reason, though I'm a Republican, I've decided to support Kamala Harris for president."
Gonzales said Trump's actions contravened "fidelity to the rule of law", including the then president's involvement in the January 6 insurrection on Capitol Hill.
Pointing to the "intoxicating" nature of power and how Trump appears unlikely to "respect the power of the presidency in all instances", Gonzales wrote:
"Perhaps the most revealing example relates to Trump's conduct on Jan 6, 2021, when he encouraged his followers to march to our nation's capital in order to challenge the certification of Joe Biden's electoral victory."
Gonzales continued: "Trump failed to do his duty and exercise his presidential power to protect members of Congress, law enforcement and the Capitol from the attacks that day. He failed to deploy executive branch personnel to save lives and property and preserve democracy. He just watched on television and chose not to do anything because that would have been contrary to his interests."
He also noted Trump's felony convictions, his civil liability for libel based on a sexual abuse, the pending federal elections interference case and the recently dismissed federal documents case, which he noted that the special counsel Jack Smith is continuing to pursue.
Notably, Gonzales did not raise Harris's policy track record as a reason for voting for her, writing in fact that she does not "not have the same depth of experience in foreign policy or the relationships with foreign leaders that Biden has".
Nevertheless, he called on the American public to "place their faith in her character and judgement", saying that based on her speech at the Democratic national convention and her debate performance against Trump on Tuesday evening, she was "best suited, able and committed to unite us in a manner consistent with the rule of law".
Gonzales joins several other prominent Republicans who have crossed party lines and expressed their support for Harris, including the former Illinois representative Adam Kinzinger, Trump's former press secretary Stephanie Grisham, Trump's former White House communications director Anthony Scaramucci, and the former Georgia lieutenant governor Geoff Duncan.
Highest profile of all was the former vice-president Dick Cheney, who last week said he planned to vote for Harris. He joins his daughter, the former Wyoming Republican representative Liz Cheney, who also endorsed Harris.
"In our nation's 248-year history, there has never been an individual who is a greater threat to our republic than Donald Trump," he said. "He can never be trusted with power again."
