Eliza Collins

USA TODAY

Michael Chertoff, once the lead Republican counsel on the Senate committee investigating the Clintons' Whitewater land deal, is now officially backing Hillary Clinton for president.

Chertoff, who went on to become the secretary of Homeland Security under George W. Bush, told Bloomberg View over the weekend that he made the decision because of the importance of national security.

"I realized we spent a huge amount of time in the '90s on issues that were much less important than what was brewing in terms of terrorism," he said.

Chertoff also said that while the Clintons have made some mistakes they dwarf in comparison to the need for national security.

"People can go back decades and perhaps criticize some of the judgments that were made [in the 90s],” Chertoff said. "That is very, very insignificant compared to the fundamental issue of how to protect the country."

Whitewater was a probe into a land deal the Clintons were involved in shortly before Bill Clinton was elected governor of Arkansas. The investigation didn't turn up anything, but it spawned other investigations into the Clintons that wound up uncovering Bill's affair with Monica Lewinsky, leading to his impeachment by the House.

In his interview over the weekend, Chertoff addressed Clinton’s use of a private server specifically, telling Bloomberg that it was a mistake, but "she did not intentionally endanger national security."

Chertoff previously signed a letter warning of the consequences of Trump presidency to national security but his decision to publicly back Clinton came after last week’s debate.

"Trump's sense of loyalties are misplaced," he said. He added that the way Trump has handled the situation with former Miss Universe Alicia Machado — he has defended calling her “Miss Piggy” and “Miss Housekeeping” and went on a Twitter tirade in the wee hours of the morning last week — brings up concerns of impulse control.

"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. If you're president, the button you reach for is not the Twitter button; it's the nuclear button,” he said.

Earlier this month Clinton met with Chertoff and a group of other bipartisan national security officials.