Briarcliff Entertainment, the film's distributor, tells TMZ ... a 15-second advertisement for the film was rejected by both ABC and CBS from airing during debate nights.

CBS, which is hosting tonight's debate between Tim Walz and J.D. Vance, told Briarcliff the network doesn't feel comfortable promoting "The Apprentice" in the debate or during national news -- but is open to advertising the film during other parts of the day.

ABC, which hosted the presidential debate a few weeks ago, nixed the ad ... telling Briarcliff the network wanted to stay away from ads that "speak to related themes within the broadcast."

You'll recall, Trump and his team fought hard to block the release of the film, firing off a cease-and-desist letter to filmmakers in May. But, Briarcliff Entertainment ended up securing the rights and will release the film in theaters nationwide on October 11.

TMZ has obtained the 15-second ad that's been rejected by networks, which you see here.

Sebastian Stan stars as Donald Trump early in his ascent to power, eager to learn from his mentor, famed right-wing and political fixer Roy Cohn ... played by "Succession" star Jeremy Strong. In the clip, you hear Strong's character declare, "If you're indicted you're invited."

Of course, the scene that's generating the most buzz is when Stan's Trump is depicted sexually assaulting his ex-wife Ivana Trump, played by Maria Bakalova. We should note, Trump and his lawyers have denied the sexual assault claim numerous times -- which filmmakers took from Ivana's 1989 divorce deposition.