DYERSVILLE, Iowa — Bernie Sanders was warming up in shallow center field, launching balls toward the thick rows of corn that sweep across the perimeter of the “Field of Dreams” film site here in Iowa, when one of his press aides told a line of nearby reporters it was time for them to give the senator some space.

“They can stay,” Sanders snapped back, voice raised. “You guys want to stay, they can stay.”

His aides drew back and the reporters stayed put, watching the 77-year-old bat around, with all three parties looking like uneasy guests at their own event. Plans for the “Press vs. Staff” softball game, organized weeks ago and promoted by campaign officials as a public “show” of “goodwill and sportsmanship” toward the press at a time when “members of the media are demonized by the president,” collapsed late this weekend as Sanders both intensified his usual criticism of the “corporate media” and attempted to raise money off the outing by selling custom-made baseball cards. (His stats: “#46, Presidential Candidate. Home: Burlington, Vermont. Bats: Right. Throws: Right. Thinks: Left.”)

In the span of the last two weeks — as Sanders aides printed jerseys and hats, booked food trucks for the venue, and recruited the actor Susan Sarandon, star of the 1988 baseball classic Bull Durham, to make the long trip to Dyersville to serve as color commentator during the game — the Vermont senator and his aides launched a new campaign against the same reporters who were readying their Monday night roster.

He suggested the Washington Post let its owner, Amazon founder Jeff Bezos, influence coverage of his candidacy. (The baseless claim, described by the Post’s executive editor Marty Baron as “a conspiracy theory,” mirrors attacks from President Trump.) He launched a newsletter from David Sirota, a senior adviser and left-leaning investigative reporter known for his slash-and-burn presence on Twitter, aimed at bypassing traditional media. (“Bern Notice” promises readers exclusive “scoops, insights, and news nuggets” you won’t find in the press.) And his top adviser, Jeff Weaver, accused the media of engineering a widespread “Bernie Write-Off” in which news outlets, he said, ignore polls that show Sanders up. (“It’s unfortunate,” Weaver told members of the press last week. “We just want to make all of you aware.”)

A few days later, with a week before the softball game, a fundraising email warned Bernie supporters that they would have to “take on virtually the entire media establishment” in order to win.

By then, a handful of reporters were already talking about whether it would be a good idea to sit out the game. It did not cause much controversy in 2012 when Republican nominee Mitt Romney hosted an awkward but good-natured touch football match on Florida’s Delray Beach between staff and his traveling press corps. Four years later, in the more fraught campaign environment of 2016, Hillary Clinton critics on the left and right seized on an off-the-record dinner John Podesta hosted at his home in Washington, DC, where he served reporters home-cooked pasta with walnut sauce, as evidence of some secret bias.

Sanders has stoked some of that skepticism at a time when an increasing number of progressives are publicly criticizing the political media, especially over coverage of Trump and the Democratic horse race. He’s said his critique of the media is nothing like Trump’s — “I don’t think the media is the enemy of the people,” he told reporters earlier this summer, “God knows I don’t think that” — but his near daily warnings against the “mainstream,” “corporate” press have helped create the new media landscape that seems years removed from the days of Romney touch football.

The media, as Sanders describes it, is part of the same “establishment” that wants to see him lose, that treats campaigns as “political gossip,” and has no interest in covering poverty, income inequality, or the influence of big banks. In the 1980s, as a young mayor of Burlington, Vermont, he floated the idea of commanding his own five-minute spot on the local evening news to “talk directly to the people,” in the fashion of the US president’s ability to address the nation during times of crisis on network primetime, according to Greg Guma’s 1989 book, The People’s Republic. As a candidate in 2020, Sanders has achieved some of that original vision with his own “unfiltered” media content, tasking Sirota with his newsletter, livestreaming his events, and producing his own podcast, Hear the Bern.