As a rule, it is a mistake for the press to write about itself. Journalists will always find journalism fascinating. But readers are not nearly so interested in media navel-gazing. If newspapers spent each day analysing one another, readers would rapidly lose interest, and rightly so. Yet the editorial in today’s Daily Mail about the Tory party and Brexit is such a striking change of course that an exception to normal self-restraint is in order.

The headline on its leader – “Saboteurs endangering the nation” – may have seemed like normal Daily Mail fare. This was the newspaper, after all, which in its “Who will speak for England?” headline in 2016 pushed David Cameron aside and placed itself firmly at the head of the leave campaign; which used stories like “Plans to let 1.5m Turks into Britain” to make leave’s final push explicitly anti-migrant; which charged Britain’s impartial judges with being “Enemies of the people” for ruling that parliament was sovereign in the Brexit process; which welcomed Theresa May’s 2017 election launch with a call to “Crush the saboteurs”; and which, under the snarling headline “Proud of yourselves?”, excoriated 11 Tory MPs who backed a meaningful vote on Brexit for their “treachery”.

Yet the tone and, in particular, the focus of this morning’s leader were, in fact, very different from that confident in-your-face era. Instead of firing up the Brexiters for yet another act of anti-European contempt and defiance, as it had done for so long, the Mail this week turned its fire on them instead. It denounced the “arch-Brexiteers” for their “self-promotion and peacocking” and their efforts to undermine Mrs May. Former Mail heroes like Iain Duncan Smith, David Davis and Mr Johnson were dismissed as “vulgar bit-part players” and “back-stabbing plotters”, compared unfavourably with Brexit secretary Dominic Raab – “grown in stature” – and above all Mrs May, “the only person” who can secure an “acceptable outcome” and “sensible deal”.

Such language is not just a media milestone. It is also a political one. The Mail is in many ways what it was from the start in 1896: a very brilliant newspaper. But at many points in its history – from Lord Northcliffe’s warmongering before and after 1914, through its publication of the Zinoviev letter forgery in the 1920s to discredit Labour, to its support for fascism under Lord Rothermere in the 1930s, it has also been a reckless political protagonist. So it has been, once again, in our own time. The Mail has been a propagandist for Brexit and for a radical reactionary Tory tradition that looks back to empire and Margaret Thatcher as its guiding lights. The rage and aggression that marked its advocacy of Brexit were absolutely in the Northcliffe tradition. But, like him, they left an indelible mark for the worse in politics and public life. The shockingly violent remarks by Tory MPs about Mrs May this week are part of this legacy. So is the gross Brexit-derived insult to the family of a seriously sick child by Mr Davis’s former chief of staff this week.

The easy explanation for this shift would be to attribute it to the new editor, Geordie Greig, who replaced Paul Dacre last month after a 26-year reign. That is a big factor. But the deeper reason is that the national mood is changing. Brexit is becoming a burden on Britain. Doubts about the future are deepening. Last Saturday, parts of middle Britain to which the Mail does not speak took to the streets against Brexit. Today, police leaders, medicine distributors and scientists were the latest to voice Brexit concerns. Meanwhile the cabinet went on squabbling at home and Liam Fox continued chasing a fantasy trade deal with Donald Trump abroad.

Fanatics are often the last to see that their dreams have turned to nightmares. But the British public, who are not fanatics, get it. So, belatedly, does a Mail that drove so hard to the cliff edge. The message has yet to reach many Tories. But they risk being swept aside if it doesn’t. The hard Brexiters are on the run.