The growing division means that some readers are getting their news through an ever-narrowing prism. Americans who get their information predominantly from Breitbart News, a right-wing news and opinion site, for instance, or from the conservative Fox News are getting a very different version of the news from Americans who read The Washington Post or watch CNN.

Breitbart Raises Questions

Late Monday night, as the news broke that Mr. Flynn had resigned, news organizations rushed to publish articles.

Not Breitbart.

For roughly an hour after Mr. Flynn’s resignation letter began circulating, Breitbart did not change the main story on its home page, which was about immigration policy.

When Breitbart made the Flynn resignation its main story, around midnight, the account hewed closely to the facts of Mr. Flynn’s resignation and quoted heavily from his resignation letter. The site also put up a more analytical article that raised questions about the motives behind the government’s monitoring of communications between Mr. Flynn and the Russian ambassador.

“Democrats are clamoring for a deeper investigation of Russian ties to Trump,” the article said. “But the more serious question is whether our nation’s intelligence services were involved in what amounts to political espionage against the newly elected government.”

The article also raised questions about how the news media got its information, reinforcing a distrust of the press that Mr. Trump and his administration have assiduously tried to foster.

“The fact that the contents of Flynn’s phone conversation — highly sensitive intelligence — were leaked to the media suggests that someone with access to that information also has a political axe to grind,” the article said.