George W. Bush’s former speechwriter and Senior Editor of the Atlantic took to Twitter on Friday morning to express his concern over Donald Trump’s impending administration. Just hours ahead of Friday’s inauguration ceremonies, Frum called Trump the “the worst human being ever to enter the presidency.”

He added, “and I include all the slaveholders.” In a follow up tweet, the former Bush staffer wrote, “Andrew Jackson was at least physically brave.” Frum served the Bush administration from 2000 to 2002 as a speechwriter for the president.

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The worst human being ever to enter the presidency, and I include all the slaveholders. — David Frum (@davidfrum) January 20, 2017

Frum, who is from Canada, also took a moment to poke fun at Americans, writing, “Canadians waking up this AM thinking, ‘So … any 2nd thoughts about all those jokes about how boring our politics supposedly is?'”

Thousands of protestors have planned actions across the country in opposition to Trump’s inauguration, including at right-wing celebrations on the eve of the inauguration. The women’s march on Jan. 21, which is expected to be one of the largest protests in American history.