Public intellectual and documentary filmmaker Ken Burns delivers the commencement speech at Stanford University in June. Burns used his time at the podium to criticize the candidate of Donald Trump.

* This story originally aired on WGBH News on July 18, 2016.

The Republican National Convention is underway in Cleveland, and it’s likely to be one for the history books. Many of the scholars who will write that history, though, are already concerned about what they'll have to look back on if Donald Trump should win the presidency. A group calling itself Historians Against Trump has published an open letter outlining what it sees as a mission.

The manifesto says Donald Trump’s candidacy undermines the very nature of American democracy.

“We feel that the threat he poses is something bigger than just politics," said Caroline Luce, who teaches American history at the University of California, Los Angeles.

Luce helped draft the letter, which doesn't endorse any candidate outright but does say the group plans to actively oppose the presumptive Republican nominee.

“His speeches, his policies and his use of social media represent a sort of know-nothingism and blinding self-regard that we think is really dangerous to not just this election but our political discourse broadly,” Luce said.

Trump’s speeches and tweets have alternatively targeted women and Muslims and immigrants, boggling the GOP establishment.

Research shows most academics are liberal, so it's hardly a surprise that a bunch of historians would be against the Republican nominee. But even conservative scholars say the lessons of history compel them to speak out against Trump and his tone.

"Like so many others, I keep asking myself: 'How in the world can it be that the Republican Party, the party of Abraham Lincoln, is on the verge of nominating the likes of Donald Trump for president of the United States,'" said author David McCullough in a video posted to Facebook.

McCullough grew up a Republican, and until now he’s refused to talk about present day politics. 

 Earlier this month, though, the presidential historian expressed his views and put the Trump candidacy into historical perspective.

"President Dwight D. Eisenhower, who so admirably served his country his entire career, said there were four key qualities by which we should measure a leader: character, ability, responsibility and experience,” McCullough explained. “Donald Trump fails to qualify on all four counts."

Other public intellectuals and popular historians are also breaking format and protocol.

“There comes a time when I and you can no longer remain neutral, silent. We must speak up and speak out,” said filmmaker Ken Burns, addressing students and faculty at Stanford University's commencement speech last month. 

Burns prides himself on being politically neutral, but at Stanford the Hampshire College graduate delivered a blistering attack against Trump and called out the media for encouraging his rise.

"Edward R. Murrow would have exposed this naked emperor months ago,” Burns admonished. “He is an insult to our history, and do not be deceived by his momentary good behavior. It's only a spoiled misbehaving child hoping to somehow still have desert."

Other academics, though, think it's the historians who are misbehaving.

“What they’re doing is inappropriate,” said Stanley Fish, who teaches law at Florida International University.

Fish is an outspoken critic of academia, and he thinks left-leaning professors have mistaken their expertise.

“The historians are exhibiting the hubris, the pride, the arrogance that many academics exhibit when they think that the possession of an advanced degree confers on them a general wisdom,” Fish said.

Fish says the average American voter is suspicious of academics, and these letters and speeches against Trump will only fuel those suspicions.

“One part at least of the Trump appeal is the people who feel they’ve been bypassed, marginalized or even dismissed by elites – and they include academics,” Fish said.

Those academics who do harbor secret Trump leanings are unlikely to admit that they’ll vote for him because the 725 people who’ve already signed the open letter would harass them.

Earlier: At Wellesley, A Conservative, A Libertarian, And Some Liberals Walk Into A Classroom