Sean Hannity of Fox News appears at the 2016 Conservative Political Action Conference in National Harbor, Md. In Los Angeles, an ad for the new Nazi-themed documentary "A Night at the Garden" will air during his show. (Carolyn Kaster/AP)

Some viewers of Fox News Channel’s “Hannity” on Monday night will get a jolting image: scenes from a rally of American Nazis in New York.

The images are meant not as promotion but as a warning: They will come as part of a 30-second spot for “A Night at the Garden,” a new Oscar-nominated documentary short about the rally of the German Bund at New York’s Madison Square Garden in 1939. It was directed by the liberal-minded filmmaker Marshall Curry.

The ad is not a national spot. It will be seen only in Los Angeles, by viewers watching on Charter Communication’s Spectrum service, which reaches an estimated 1.5 million homes.

The short looks at the rally that attracted 22,000 people to cheer on Fritz Kuhn and other leaders of the American Nazi Party. Filmmakers have bought time during the Fox show in the hope of drawing comparisons to what they say are similar tactics by President Trump.

“It just seemed like the biggest Trump supporter on television is Sean Hannity, and many members of his audience are falling for some of the same tricks Bund leaders used in 1939 without understanding the significance of them,” Curry said in an interview. “So we decided to try to remind them that when they see leaders who attack the press and minorities and wrap it in American symbols of patriotism, it yields horrible results, to suggest that people should be vigilant about demagogues.”

He added, “The point of the spot is less about rallying people who are already worried than reaching people who don’t realize how dangerous this tactic is.”

A Fox News spokeswoman said in a statement, “The commercial in question was a local ad buy, which was done through the regional cable system, not through the network at the national level. We have no control over what airs locally.”

A network is typically directly involved only with national ads, which it books directly. Local ads, which usually get several minutes of time in a given broadcast, are sold by cable providers. Those companies generally flag content only for explicit material, and they and the networks do not typically communicate about every ad taken in every market, which can run in the hundreds on any given night. This can sometimes lead to misunderstandings, tension and even accusations of an end run, as when the Church of Scientology took local ad time during the 2013 Super Bowl that some viewers mistook for a CBS-sold Super Bowl ad.

The short film is backed by Field of Vision, the New York-based documentary company co-founded by “Citizenfour” director Laura Poitras and part of First Look Media, which Poitras founded with the journalists Glenn Greenwald and Jeremy Scahill. The ad will include footage from the film as well as guidance about where to watch it.

There is no reference to the current political climate in the film or the ad. Still, the filmmakers’ candor about their reasons for making the movie, combined with an ad on a conservative cable show, could be read in some quarters as comparing Trump supporters to those at the arena that night.

Curry said that he and his producers got no pushback from Spectrum when booking the ad, which was done by the agency Sawyer Studios on behalf of the marketing and publicity arm of Cinetic Media, a New York film company. The ad will air in Los Angeles only instead of national markets because the film’s marketing budget precluded a more expensive buy, a Cinetic executive, Anna Barnes, told The Washington Post. A staffer at Sawyer, Mike Lawson, on Monday evening confirmed there was no pushback from Spectrum and the ad was scheduled to run Monday night in Los Angeles.

Charlotte Cook, another co-founder of Field of Vision, said the “Hannity” spot was intended in the spirit of conversation, not confrontation.

“We’re very aware that the film audience can often lean to the left,” she said. “And we want to make sure this film doesn’t go to the echo chamber — to use this moment of the [Oscar] nomination to jump the barrier to people with different beliefs.

“We want to make as many people as possible aware that things can so easily spiral in ways they didn’t intend when they voted.”

Curry learned about the material, which was housed at various places, including the National Archives and UCLA’s film school, from a screenwriter friend, then set about acquiring and editing it. Nearly all the footage inside the arena, he said, was shot by the Bund.

The director had embarked on the project in early 2017 before news events changed the tenor of his work.

“When I started making this movie, it was before Charlottesville, and I just wanted to say something about demagoguery in general, which Trump is one of the most effective practitioners of,” said Curry, who has previously been nominated for two Oscars, including for “Street Fight,” a 2005 look at then-Newark mayoral hopeful Cory Booker. “And then when Charlottesville happened, I thought, ‘This is no longer a metaphor.’ ”

Subsequent news events, such as a mass shooting at Tree of Life synagogue in Pittsburgh, have made it more timely, he said.

The film has been distributed online in recent months and has had several limited theatrical runs. It has gotten a boost with the Oscar nomination several weeks ago. Reviews have been strong, and it is considered a front-runner to win the prize at the ceremony in Los Angeles on Feb. 24.

The spot also comes amid a debate over anti-Semitism among congressional Democrats in the wake of Rep. Ilhan Omar’s remarks, since apologized for, that Republican support of Israel on Capitol Hill was “all about the Benjamins,” and it could spark criticism that it is unfairly targeting the right on these issues.

Curry said he hopes the film addresses intolerance in all its forms but said he felt the Bund rally had particular overtones to the White House’s current occupant.

“It’s my hope this film, by showing the history, will alert people to the dangers in the present time, wherever they may come from,” he said. “But the way a leader attacks the press, attacks minorities, puts a casually humorous spin on violence against protests — that felt particularly Trumpian."

Editors note: The headline was changed to make it clear the ad was a local one. Fox News’ statement, in which it stated it does not control what airs locally, was moved higher in this story.