Rupert Murdoch, hitherto one of Donald Trump’s most loyal media messengers, appears to have turned on the former president.

US media circles were rocked this weekend after the New York Post issued an excoriating editorial indictment of Trump’s failure to stop the attack on the US Capitol on 6 January 2021.

The editorial, in a tabloid owned by Murdoch since 1976, began: “As his followers stormed the Capitol, calling for his vice-president to be hanged, President Donald Trump sat in his private dining room, watching TV, doing nothing. For three hours, seven minutes.”

Trump’s only focus, the Post said, was to block the peaceful transfer of power.

“As a matter of principle, as a matter of character, Trump has proven himself unworthy to be this country’s chief executive again.”

The Wall Street Journal, another Murdoch paper, issued a similar critique in which it said evidence before the House January 6 committee was a reminder that “Trump betrayed his supporters”.

Trump, the Journal said, took an oath to defend the constitution and had an obligation to protect the Capitol from the mob he told to march there, knowing it was armed.

“He refused. He didn’t call the military to send help. He didn’t call [Mike] Pence to check on the safety of his loyal [vice-president]. Instead he fed the mob’s anger and let the riot play out.”

Trump had “shown not an iota of regret”, the Journal said, adding: “Character is revealed in a crisis, and Mr Pence passed his January 6 trial. Mr Trump utterly failed his.”

The editorials were only the latest salvos from the big guns of Murdochian conservatism.

“The person who owns January 6 is Donald Trump,” the Journal said in June.

“Look forward!” it urged readers. “The 2024 field is rich. You have Florida governor Ron DeSantis, former secretary of state Mike Pompeo, former UN ambassador Nikki Haley … the list goes on. All candidates who embrace conservative policies … Unsubscribe from Trump’s daily emails begging for money. Then pick your favorite from a new crop of conservatives. Look to 2022, and 2024, and a new era. Let’s make America sane again.”

Columnists issued similar calls.

“Let go of the anvil that, in the most buoyant waters imaginable, will sink you to the bottom of the sea,” Peggy Noonan wrote in the Journal.

In the Post, Michael Goodwin said Trump’s “old feuds and grievances already sound stale and by 2024 they are not likely to inspire the hope and confidence America desperately needs”.

Last year, Murdoch himself said conservatives must play an active role in political debate, “but that will not happen if President Trump stays focused on the past”.

There are also signs that Murdoch’s most powerful media property, Fox News, is beginning to change its stance. On Friday, Fox News elected not to broadcast a Trump rally in Arizona during which a state endorsement met with boos. Instead, Fox News broadcast an interview with DeSantis.

Observers believe Murdoch, 91, may be tiring of Trump’s lie that the 2020 election was stolen, which has both kept Trump in the spotlight and denied him the ceremonial status usually extended to ex-presidents.

Murdoch outlets have faced legal repercussions for repeating Trump’s lie. A judge in Delaware recently said Fox Corp could be sued by Dominion Voting Systems for broadcasting conspiracy theories related to the 2020 election.

Rupert Murdoch and his son Lachlan are named in the $1.6bn suit, for allegedly acting with “actual malice” in allowing Fox News to broadcast claims the election was rigged. The judge, Eric Davis, cited reports that the elder Murdoch privately said Trump lost the election.

Fox News says it is “confident we will prevail as freedom of the press is foundational to our democracy and must be protected, in addition to the damages claims being outrageous, unsupported and not rooted in sound financial analysis, serving as nothing more than a flagrant attempt to deter our journalists from doing their jobs.”

A friendship of convenience

The relationship between Murdoch and Trump has long been regarded as one of convenience. Thirty years ago, Trump often used the New York Post in his divorce battle with Ivana Trump, his first wife who died this month. As described by the Trump ally Roger Stone, to the New York Times, Trump considered the Page Six column “very important to his rising stature in New York City and branding efforts”.

But a year before Trump was elected, in 2015, the Times reported that Murdoch thought him a “phony”.

After Trump mocked the senator and former Republican presidential nominee John McCain, Murdoch wrote on Twitter: “When is Donald Trump going to stop embarrassing his friends, let alone the whole country?”

The Journal called Trump a “catastrophe” and declared: “Trump is toast.” But by the time Trump was elected in 2016, he and Murdoch had cemented a friendship of convenience.

Murdoch was able to bypass White House aides to reach the president. Trump reportedly called Murdoch for reassurance Fox News would not be affected by a deal to sell 21st Century Fox to Disney.

Jared Kushner and Ivanka Trump holidayed on Murdoch’s 184ft yacht. Ivanka became a trustee for Murdoch and Wendi Deng’s twin daughters.

The latest editorials may not change the views of Fox News primetime hosts. Sean Hannity, for one, has described the House January 6 hearings as an “obsessive partisan anti-Trump smear” and claimed they have not “establish[ed] a criminal case or reveal[ed] new damning evidence … as they have promised”.

But the print titles seem to be moving on. Quoting “someone in the Murdoch orbit”, Vanity Fair said last month the media baron was “a pragmatic guy”.

“He knows better than anybody how to read political tea leaves. It’s fairly self-evident that quite a few people in the firmament have begun to challenge the previously supported collective viewpoint about Trump. It’s understood now that the gloves are off. As [Trump] lashes out, it just makes it easier for people to hit back.”