“Trump’s election would threaten our democracy,” Summers wrote for the Washington Post. “Even the possibility of Trump becoming president is dangerous.”

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While Summers stops short of agreeing that the presidential contender ranks with some of history’s most infamous demagogues—”overwrought,” he calls the comparisons—he set the piece’s tone by name-dropping Benito Mousilini and Adolf Hitler in the opening sentence.

“The possible election of Donald Trump as president is the greatest present threat to the prosperity and security of the United States,” he wrote, before proceeding to fire off a litany of what he deems to be some of the candidate’s worst offenses. These include insulting women, pledging to “take out” terrorists’ families, supporting waterboarding, and banning Muslims from entering the country, among other things.

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According to Summers, both the global economy and the nation’s geopolitical relations would suffer as a result of a Trump presidency. Electing a protectionist to office would, he argued, force people to lose confidence in markets at home and overseas, and could spark a worldwide recession. He also said that a more “erratic” and “isolationist” America would lose ground in its standoff with China over influence in Asia.

“The United States has always been governed by the authority of ideas, rather than the idea of authority,” he wrote. “Nothing is more important than to be clear to all Americans that the tradition of vigorous political debate and compromise will continue. The sooner Donald Trump is relegated to the margins of our national life, the better off we and the world will be.”

Read more: “Welcome to the United States of Donald Trump”

Fortune has reached out to Trump’s campaign for comment. We will update this post if we hear back.