When the filmmaker Ken Burns and the Pulitzer Prize-winning author David McCullough asked David Levering Lewis to make a video criticizing Donald J. Trump, Mr. Levering Lewis thought it was "a jolly good idea."
With a friend recording the video on his iPhone, Mr. Levering Lewis remarked that Mr. Trump’s staying power derives from "free association of reckless solutions to immigration, domestic terror, and whatever else comes to mind, along with verifiably absurd reiterations of disparaging untruth."
The four-minute video was posted on the Facebook page that Mr. Burns and Mr. McCullough created, Historians on Donald Trump. The video, which sits alongside similar clips by more than two dozen American historians, had gained more than 6,000 views by Wednesday afternoon.
"I remember thinking that it’s certainly appropriate that if a Supreme Court justice can deviate from the usual proprieties of her role, certainly historians can join Justice [Ruth Bader] Ginsburg in opining about this extraordinary political season," Mr. Levering Lewis, a professor of history at New York University, said in an interview. Justice Ginsburg, who later apologized, said in a New York Times interview this month that she "can’t imagine what the country would be — with Donald Trump as our president."
Mr. Levering Lewis’s video is among a number of efforts by historians to take on the Republican presidential nominee. Several scholars who have participated in those efforts, under campaigns known as Historians on Donald Trump and Historians Against Trump, say they are not seeking to sway voters or to speak out on what they see as the right side of history. Instead, they see it as their duty to point out historical precedents for a Trump presidency and to help the public make educated choices.
"I’m not sure whether historians mobilizing to put evidence out there is really helpful," said Claire Potter, a professor of history at the New School who signed the open letter that Historians Against Trump used last week to announce its formation and outline its mission. "But I think if we didn’t," she added, "it would be remiss of us."
Ms. Potter, who wrote the blog Tenured Radical, said that one particular excerpt from the letter moved her to sign: "Our profession reminds us to look for the humanity in everyone as we examine the ideas, interests, and movements that shape world events."
More than 940 people had signed the letter on the Historians Against Trump website and on a separate iPetitions page by Wednesday afternoon.
In his video, Mr. Levering Lewis contrasted Mr. Trump with Wendell Willkie, a businessman who had never held political office but ran and lost to Franklin D. Roosevelt in the 1940 presidential election. Although Mr. Trump and Mr. Willkie may appear similar on the surface, Mr. Levering Lewis said, Mr. Willkie had greater integrity and appealed more to bipartisanship.
Vicki Lynn Ruiz, a professor of history at the University of California at Irvine, took part in both campaigns: She signed the Historians Against Trump letter and made a video for Historians on Donald Trump in which she compared Mr. Trump’s views on Mexican immigrants to the sentiments behind the deportation and repatriation of Mexicans during the 1930s.
"The reason why the rhetoric alarms me is that in our history there are the marks of prejudice and exclusion," she said in an interview. "It’s playing to what I think are inflammatory politics: Jim Crow, Asian exclusion, Mexican deportation, Japanese-American internment. I think this kindling of fear is really propelling us backward and not forward as a nation."
Mr. Levering Lewis is not sure that the endeavors of Historians on Donald Trump will make much difference in the election, but he’s optimistic.
"That is to say, if I thought it was pointless, I wouldn’t have signed on," he said.
Some scholars, however, object to some of their peers’ efforts to call out Mr. Trump.
Stanley Fish, a professor of law at Florida International University, slammed the Historians Against Trump letter in an op-ed in The New York Times titled "Professors, Stop Opining About Trump."
"Academic expertise is not a qualification for delivering political wisdom," he wrote.
Jonathan Zimmerman, a professor of the history of education at NYU, wrote a commentary for The Chronicle criticizing the movement as well.
He took aim at the Historians Against Trump group’s assertion that Mr. Trump’s candidacy is an attack on the historians’ profession. He argued that the claim "is itself a repudiation of our professional values, which enjoin us to understand diverse communities instead of dismissing them as warped or deluded."
David Schlitt, a historian in Pittsburgh who is on the organizing committee of Historians Against Trump, defended his group in an interview.
"There are historical lessons to be applied and learned," he said. "This idea that we’re trying to end a conversation and persuade voters is quite different from what we’re all doing, which is to start a conversation and ask people to do their own research and their own explorations into the subject."
Ms. Potter said that two past presidents of the United States, Woodrow Wilson and Theodore Roosevelt, were also past presidents of the American Historical Association and that "both felt very deeply that historians have a role to play in politics."
She called Mr. Trump a threat to her profession, which she wanted to leave a mark on "as I knew it and understood it."
Mr. Levering Lewis said that efforts like Historians on Donald Trump can foster well-informed debate and he hopes that citizens will recognize people who misrepresent issues in politics.
He compared Mr. Trump to another man who made an improbable rise to power over a country, this time in Germany in 1932. That man, too, was called an extremist, but he was not taken seriously enough before it was too late, and German democracy was destroyed.
"And the rest," Mr. Levering Lewis said, "is history."