To political reporters, Mr. Jacobs’s experience seemed the troubling next step in a growing trend.

“Sadly, shamefully, disgustingly, it has come to this,” lamented Gene Policinski, an executive at the Newseum in Washington. The Reporters Committee for Freedom of the Press also condemned the rough handling of Mr. Jacobs, calling the recent spate of incidents involving reporters “an assault on the very core of democratic life.”…

“There are people who are listening to this dog whistle,” said April Ryan, the White House correspondent for American Urban Radio Networks. She recalled a hot-mike moment last week where Mr. Trump and his Homeland Security secretary, John Kelly, were overheard joking about using a ceremonial saber on the press.

“It is not cool,” Ms. Ryan, who encountered brusque treatment herself at a White House press briefing, said in an interview. “Who are we? Are we a third-world country? You cannot persecute the press for asking questions about the truth.”