A top official in the George W. Bush administration has become the most prominent Republican to endorse Hillary Clinton for president.

Richard Armitage, who was Bush's deputy secretary of state during his first presidential term, told Politico in an article published Thursday that Trump "doesn't appear to be a Republican, he doesn't appear to want to learn about issues. So I'm going to vote for Mrs. Clinton."

Armitage, who also served under President Ronald Reagan, isn't the first Republican to throw his support behind Clinton.

Arne Carlson, the Republican former governor of Minnesota, told CityPages on Wednesday that "no human being in history has been more vetted" than Clinton while Trump "has taken campaigning to a new low."

Mike Treiser, a former Mitt Romney staffer, said that "in the face of bigotry, hatred, violence, and small-mindedness, this time, I’m with her."

As conservative writer Ben Howe put it, "I am a fiscal conservative and I am a social conservative. That will not change. But I will not vote for an egomaniacal authoritarian. Nope."

Other Republicans haven't gone as far as endorsing Clinton, but have said they can't support Trump either. Maryland Gov. Larry Hogan (R) is one of them. He's planning to choose a write in candidate instead.

Rick Wilson, a veteran GOP consultant, has even become a de facto leader of the conservative branch of the anti-Trump effort.

9/ There is no better Trump. There is not Presidential Trump. He is a vile stain on the this Republic. — Rick Wilson (@TheRickWilson) June 16, 2016

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.