The liberal megadonor George Soros is, at one point, falsely depicted as a possible Nazi collaborator, and chattel slavery is described as a byproduct of socialist economic policy. Other contradictions include sections where President Andrew Jackson, a Democrat, is said to have inspired the genocidal policies of Nazi Germany, and Southern confederates are portrayed as treasonous. These parts leave out that Mr. Trump, the film’s hero, has cited Jackson as an inspiration, and that Mr. Trump’s chief of staff has defended Confederate general Robert E. Lee as an “honorable man.”

In Mr. D’Souza’s film, the president is a liberator blessed with Abraham Lincoln’s “inner toughness,” currently “saving America” from the “new Democratic plantation” of “black ghettos, Latino barrios, Native American reservations.”

Mr. D’Souza pleaded guilty to charges of making illegal campaign contributions in 2014, but was fully pardoned by Mr. Trump in late May.

“The stakes could not be higher,” Mr. D’Souza says at one point in the film. “Read the Nazi platform at the Democratic convention and it would most likely receive thunderous applause.”

Such inflammatory rhetoric has not stopped “Death of a Nation” from reaching the upper echelons of the Republican Party. Mr. D’Souza recently held a glitzy reception for the movie in Washington, complete with celebrity red carpet appearances from Donald Trump Jr., the president’s son, and Housing Secretary Ben Carson. The re-election campaign of Representative Kevin Brady, the chairman of the House Ways and Means Committee, held a watch party in Woodlands, Tex., in July. The movie has thus far grossed about $4.5 million, and several of Mr. D’Souza’s previous films rank among the highest-grossing American political documentaries of all time. (His conspiratorial 2012 film about President Barack Obama made more than $30 million, and is one of the highest-grossing domestic documentaries in the United States in decades.)

Lynda Bowers, the affable president of the Medina County Republican Women group, prepared goody bags for audience members that included a pocket constitution, some prewrapped popcorn, and copy of one Mr. D’Souza’s previous movies — which include a 2016 film targeting Hillary Clinton and the 2012 movie, tagged “Obama’s America: Love Him. Hate Him. You Don’t Know Him.”