Former Bush DHS chief Michael Chertoff endorses Hillary Clinton

Michael Chertoff, who was once one of Hillary Clinton's biggest adversaries, will vote for her this November.

Chertoff was the lead Republican counsel on the Senate Whitewater Committee in 1995 and 1996, one of the first major congressional investigations the Democratic presidential nominee faced. The Whitewater real estate probe led Congress to President Bill Clinton's affair with Monica Lewinsky.

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Clinton later voted against him in 2001 and 2003 when Chertoff was nominated to lead the Justice Department's criminal division and to sit on the U.S. Court of Appeals, respectively. She was the lone "no" vote in each case, though she voted for him in 2005 when he was nominated to become George W. Bush's second secretary of the Department of Homeland Security.

Chertoff said his decision ultimately came down to national security. Clinton "has good judgment and a strategic vision how to deal with the threats that face us," he said.

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The stakes are too high to leave national security to Donald Trump, who lacks the knowledge and temperament necessary to be president and whose "sense of loyalties are misplaced," he said.

Chertoff signed a September letter warning that Trump lacked the skills necessary to be president, but it wasn't until last week's debate that he decided to cross party lines and publicly support Clinton.

He referenced Trump's remarks on Russia, saying they amounted to "making enemies of your friends and cozying up to your adversaries," as well as Trump's criticism of former Miss Universe Alicia Machado.

"Not only did he seem at the debate to lose his temper, but to get up at 3:30 a.m. and reach for your smartphone is to me a hysterical reaction," Chertoff said. "If you're president, the button you reach for is not the Twitter button; it's the nuclear button."

Chertoff joins several top Republicans endorsing Clinton this year. Notables include former national security adviser Brent Scowcroft, former Commerce Secretary Carlos Gutierrez, former Treasury Secretary Henry Paulson and former Deputy Secretary of State Richard Armitage. Former President George H. W. Bush will also apparently cast his ballot for Clinton.

In August, 50 senior Republican national security officials signed a letter claiming Trump "would be the most reckless president in American history."

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