Efforts to contact Mr. Bongino and Mr. Levin were unsuccessful. Mr. Shapiro, who said in an email on Monday that he had neither heard from Cumulus executives nor received a memo about coverage of election results, declared in October that he planned to vote for Mr. Trump but has also repeatedly stressed that the president has not produced evidence of voting fraud.
Brian Rosenwald, the author of “Talk Radio’s America” and a scholar in residence at the University of Pennsylvania, noted that talk radio has been “a massive force on the right” since the late 1980s, when Rush Limbaugh, a backer of the president’s baseless election-fraud claims, was ascendant, and was a key to Mr. Trump’s political rise.
“Base voters wanted someone who sounded like their favorite hosts, and Trump was just using the talk radio playbook,” Mr. Rosenwald said. “A lot of the anger on the right that is channeled into Trump was something hosts were picking up in their audiences and voicing long before Trump came along.”
Ray Appleton, a talk radio host in Fresno, Calif., was suspended by the Cumulus-owned central California station KMJ after saying on his Thursday show that “certain news editors should be hanged, maybe,” The Fresno Bee reported.
The Cumulus memo is part of a wave of censure from corporate America, one that has included banks and blue-chip businesses distancing themselves from the president and his allies, and social media companies throwing agitators off their platforms.
“Cumulus has a big, broad set of interests — they have advertisers, sports contracts, nonconservative podcasts, dealings with the F.C.C. over station licensing,” Mr. Rosenwald said. “They understand that if you get involved in something that risks instigating violence, there’s a serious danger to the bottom line.”
Sarah Sobieraj, a sociology professor at Tufts University, said that recent events offered an opportunity to rethink how “hyper-ideological spaces” are used to spread information.
“We may have seen the business model that relied on making people feel angry and afraid to drive attention reach its breaking point,” she said. “Media folks far and wide are probably asking the same questions: Could we be alienating members of the audience, losing investors and advertisers? We can’t just keep amping up.”