Politicians have long deflected criticism onto the news media, blaming it for not covering them the way they want. But the frequency and tenor of the Sanders campaign’s critique is unusual, a can’t-miss leitmotif alongside “Medicare for all,” the Green New Deal, the millionaires and the billionaires.

“I am not a candidate of the corporate media,” Mr. Sanders has said.

A particularly visible contributor to this effort is Mr. Sirota, who even while working as a journalist seemed to delight in trolling the media from inside the house. Accepting the 2015 Izzy Award for special achievement in independent media (it is named for the radical muckraker I.F. Stone), Mr. Sirota spoke of doing hard-hitting investigations “at an outlet that allows you to do it, which tend not to be legacy media outlets.”

But assailing the mainstream media could prove tricky for the campaign. A recent Pew study found that 76 percent of Democrats believe journalists act in the public interest; many support what they see as the ferreting out of executive office malfeasance. Mr. Trump, highly unpopular among voters who will choose the Democratic nominee, routinely demonizes the press, labeling it “the enemy of the people” and attacking individual outlets in strikingly personal terms.

“I think it’s politically naïve,” Todd Gitlin, a professor at the Columbia Journalism School and a prominent liberal writer, said of Mr. Sanders’s press criticism, “but also analytically misguided, and overlooking the significance of the investigations that the news media have delivered in the last three years.”

The publisher of the progressive magazine The Nation, Katrina vanden Heuvel, who has endorsed Mr. Sanders’s broader media critique, sees the challenge in the senator’s approach. “I do think it’s tricky just to attack media,” she said. It works best, she added, when “he does it with a humane criticism that millions of Americans are being shorted in terms of the coverage of their own lives and communities.”

Those associated with the campaign would insist that the Trump critique and the Sanders critique are substantively different.