War reporting has never been more dangerous, as correspondents are increasingly treated not as neutral observers but legitimate targets. Now there are signs that Donald Trump and his Republican supporters are taking a similar attitude to political journalists, casting them as enemy combatants and fair game for character assassination.

The US president’s allies are reportedly carrying out “oppo research” – usually reserved for rival politicians – to compile dossiers on individual reporters in an attempt to discredit them. It is the latest front in Trump’s war on the media, which he has identified as a bigger adversary even than political challengers in next year’s election.

“Our real opponent is not the Democrats, or the dwindling number of Republicans that lost their way and got left behind, our primary opponent is the Fake News Media,” Trump tweeted this week.

The Axios website reported Trump’s supporters are seeking to raise at least $2m to investigate reporters and editors of the New York Times, Washington Post and other media organizations, according to a three-page fundraising pitch.

“The group claims it will slip damaging information about reporters and editors to ‘friendly media outlets’, such as Breitbart, and traditional media, if possible,” Axios said.

Both Axios and an earlier report in the New York Times identified Arthur Schwartz, a Republican consultant close to Donald Trump Jr and Steve Bannon, as a leading figure in the effort to take out and potentially end the careers of journalists perceived as critical.

His Twitter account is strewn with pro-Trump sentiments and attacks on the press. This week alone he tweeted attacks on CNN and the Washington Post reporter Philip Rucker, as well as a link to a Breitbart News column by Katrina Pierson, a senior Trump campaign adviser, that began: “The Trump administration is exposing the perfidy of the mainstream media like never before.”

Sam Nunberg, a strategist for the Trump 2016 campaign, said he does not know whether the effort would focus primarily on compromising social media posts or delve into their private lives, marital histories, affiliations to certain organizations and family members with political connections.

“Going through social media posts is fair game,” Nunberg commented. “I’m not talking about going through individuals’ credit history or criminal history. But social media posts? I don’t see it as a big deal.”

He pointed to an incident last month when Breitbart News published antisemitic and racist tweets posted a decade ago by Tom Wright-Piersanti, now a politics editor at the New York Times. A link to it was tweeted by Schwartz then retweeted by Donald Trump Jr, who has 3.8 million followers, and widely circulated on conservative media.

Wright-Piersanti apologised and deleted the tweets. But Schwartz responded threateningly: “If the @nytimes thinks this settles the matter we can expose a few of their other bigots. Lots more where this came from.”

Trump’s has long had a tempestuous and incestuous relationship with the media. He shot to new levels of fame with the help of the New York tabloids and the reality TV show The Apprentice, but since entering politics he has resented scrutiny and turned his fire on the media, constantly lambasting it as “fake news” and the “enemy of the people”. The effort is widely seen as an attempt to sow distrust in media outlets and delegitimize journalists, reporting and even facts themselves.

There are signs that, with the media increasingly willing to call out lies and his polls flagging as the 2020 election approaches, Trump is intensifying the anti-media blitzkrieg. The notion of reporting on reporters has provoked alarm among political commentators and freedom of speech advocates.

Kurt Bardella, a former spokesman for Breitbart News and congressional Republicans, said: “Time and again the president’s tactic is to try to undermine the message so the facts are not deemed credible by his supporters. If this effort delves into the personal lives of reporters, that’s crossing a line because it has nothing to do with their work as reporters.”

A supporter attends Donald Trump’s campaign rally in Florida in 2017. Photograph: Alamy Stock Photo

Traditionally American presidents have shrugged off press criticism at home and championed it as a democratic ideal when overseas. But the approach of Trump and his allies designates the media as just another partisan player on the political battlefield.

Suzanne Nossel, chief executive of PEN America, said: “There has been a recognition that the press has its own role, that they’re not a political contenders, that they’re aiming to show neither fear nor favor and that they need a zone of autonomy in which to carry out their work. ”

Nossel added: “It’s insidious, it’s aimed to intimidate, it’s a kind of dragging through the mud effort, a character assassination from as best as we can tell, and it’s alarming. We need the press to do its job. We depend on them to hold politicians to account, to cover what’s going to be a very fractious campaign.

“If they have to live in fear that their personal lives or ancient communications are going to be dredged into the open in an effort to discredit them and destroy their career, who wants to work under that kind of cloud? The idea that this is being carried out by individuals who are associated with the administration or the campaign makes it all the more sinister.”

Not for the first time, Trump appears to be reaching for a playbook once used by Richard Nixon, whose vice-president, Spiro Agnew, once dismissed the press as “nattering nabobs of negativism”. Nixon and his cohorts tried to abuse the federal licensing process to pressure TV networks and kept an “enemies list” that included journalist Daniel Schorr.

John Farrell, author of Richard Nixon: The Life, said: “The actions of the current president are very much reflections of actions made by a previous president that he has said he much admires and that is Nixon, right down to the phrase ‘the press is the enemy’. There’s a famous White House tape where you have Nixon telling [Henry] Kissinger, write on the blackboard over and over again, ‘the press is the enemy, the press is the enemy’.”

He continued: “If you listen to the tapes, they talk a lot about going after individual reporters with their personal foibles, but talking it about on the tapes and actually doing it was different.”