Yet several factors have converged to elevate the practice: Fake news and false information about politics have proliferated; the public’s trust in the mainstream media is low; and social media platforms make unfiltered messaging easier than ever. As a result, there is a new urgency among politicians to deliver talking points directly. Some two-thirds of Americans get at least some of their news on social media, according to a recent Pew Research Center report.

“Bernie and others are trying to find other ways that they can more directly connect with people,” said Guy Cecil, the chairman of Priorities USA, a Democratic “super PAC.”

Many politicians blame the news media for the shift, claiming dishonest coverage has left them no other choice.

“For those of you who want to truly see what is happening, follow along through social media,” Gov. Matt Bevin of Kentucky, a Republican and a prolific purveyor of Facebook videos, told voters during his state of the commonwealth address last year. “With all due respect to what now passes for traditional media, it’s dying for a reason.”

In April, after Mr. Bevin suggested to reporters that teachers joining walkout protests were leaving children vulnerable to sexual assault, he issued an apology not in a press statement or at a news conference, but in a video that he posted on Facebook and Twitter. “A tremendous number of people did not fully appreciate what it was that I was communicating,” he said.

The tactic has vexed many of the state’s journalists, who say they have been largely shut out. “He doesn’t like to be questioned,” Al Cross, who teaches journalism at the University of Kentucky and is a columnist and former chief political reporter for the Louisville Courier Journal, said in an interview.