A group of 50 prominent Republican foreign policy and national security experts have signed a letter denouncing Donald Trump's presidential candidacy and pledging not to vote for him, CNN reported Monday.
The letter warns, according to the report, "We are convinced that in the Oval Office, he would be the most reckless President in American history."
Its signatories include former CIA and National Security Agency Director Michael Hayden, former Director of National Intelligence and Deputy Secretary of State John Negroponte and Eric Edelman, who was Vice President Dick Cheney's national security adviser and has worked closely with Michele Flournoy -- a candidate for secretary of defense in a prospective Clinton administration -- to forge a centrist group of defense experts on key military issues.
It also includes two Homeland Security secretaries under former President George W. Bush, Tom Ridge and Michael Chertoff, and Robert Zoellick, a former World Bank president, U.S. trade representative and deputy secretary of state.
The Trump campaign could not immediately be reached for comment.
Many of the same leaders wrote an open letter in March during the Republican primaries condemning Trump and pledging to oppose his candidacy, at a time when other GOP candidates remained in the race.
The letter acknowledges that many Americans "have doubts about Hillary Clinton, as do many of us."
"But Donald Trump is not the answer to America's daunting challenges and to this crucial election," it says, according to CNN.
In the new letter, the group warns Trump "lacks the temperament to be President."
"He is unable or unwilling to separate truth from falsehood. He does not encourage conflicting views. He lacks self-control and acts impetuously. He cannot tolerate personal criticism. He has alarmed our closest allies with his erratic behavior," the letter quoted by the news network claims.
"All of these are dangerous qualities in an individual who aspires to be President and Commander-in-Chief, with command of the U.S. nuclear arsenal."
The letter was published on the same day that Evan McMullin, a CIA veteran and chief policy director of the House Republican conference, announced he’s launching an independent presidential bid.
McMullin’s campaign will have the support of key players in the GOP’s anti-Trump movement, including veteran Republican strategist Rick Wilson, who has been an outspoken Trump critic.