That sound you can hear is the whirr of 650 adding machines. At Westminster, MPs are totting up the costs, tallying the benefits and working out the balance of their own interests. On the Tory benches, they know a moment of decision is coming but they can’t be sure that moment is now. Does the resignation in disgust by one of Boris Johnson’s most loyal lieutenants signal the end times, or was Munira Mirza a backroom aide no voter had ever heard of? What if both things are true? They think, chiefly, about their own seats. Their inboxes are bulging with constituents’ fury, but they hesitate before casting aside the winner of their biggest election victory for more than 30 years. Some long for the dilemma to be resolved for them, perhaps by a development so dramatic – police action or the emergence of a damning photograph, or if an unexpurgated Sue Gray report turns out to be full of what one ex-minister calls “tawdry detail” – that a consensus will rapidly form that the Johnson show is over. The bandwagon will start rolling and they’ll be able to jump on it safely. But what if there is no such moment of clarity? The minds of those at the top click and whirr with their own reckonings. The two current frontrunners have different views of time. It would suit Rishi Sunak for things to come to a head soon: he needs a leadership contest to happen before his brand is permanently tainted by the cost-of-living crisis, surging energy bills, painful tax rises and increased interest rates. Witness the front pages of the Telegraph and the Sun putting Sunak’s face alongside the words “The big squeeze” and “OUCH!” Liz Truss is happy for things to drag on for the very same reason. Labour is hardly a disinterested observer. It, too, is consulting its electoral calculator, looking at polls that show Keir Starmer ahead of Johnson, with the outlook less certain if the Tories pull off their old trick of picking a new boss and claiming to be a new government. Talk to Westminster folk and you will pick up all these noises. But all too few MPs, certainly on the Conservative benches, realise that they’re listening to the wrong part of their brains. For this stopped being a matter of calculation weeks ago. It should instead be a matter of conscience. That was true as soon as it became obvious that Johnson broke the very lockdown rules he had imposed on everyone else. But one incident this week made it clearer still. The clarity came from a single remark thrown across the dispatch box by Johnson as he sought to deflect attention from the Sue Gray “update” that, even in its gagged form, confirmed “failures of leadership” at No 10. In that remark, Johnson revealed that he is a man who will do or say anything to cling to power, no matter the cost. There is no depth to which he will not sink. The words were directed at Starmer, whom Johnson accused of “failing to prosecute Jimmy Savile”. As Mirza wrote, this was a “scurrilous accusation”, as well as “an inappropriate and partisan reference to a horrendous case of child sex abuse”. It was also demonstrably false. Nazir Afzal, a former colleague at the Crown Prosecution Service, which Starmer led between 2008 and 2013, has said that the key decision on the Savile case was taken by others before Starmer ever got there. Johnson knew that. That’s why Mirza and others had begged him not to make such an accusation. But Johnson did it anyway. No one can pretend to be surprised. This has been part of the Johnson modus operandi for years. He didn’t need Lynton Crosby to teach him about dead cats. He himself spoke openly about his technique: when besieged by scandal, the best defence is more scandal. Keep throwing out “chaff”, make ever more outrageous statements, which the press will dutifully report and, before you know it, everyone will have forgotten your original misdemeanour. Those Tory MPs deluding themselves that Johnson will change, that he now “gets it”, need to face the reality that Johnson will keep doing this – not least because it works. For much of the last week, we were indeed talking not about parties and cake, but Starmer and Savile – those two words unwarrantedly and falsely linked in the same sentence, repeated on news bulletins and phone-in shows, sneaking past the unwary listener and settling in a part of the collective brain where the specifics and the truth soon become hazy. It was the same with £350m and the EU, the very falsity of the proposition ensuring its repetition and amplification. The effect is poison. For the Savile-Starmer lie has long been a meme on the wilder shores of the conspiracy-theorist far right, where it echoes the QAnon lunacy with its suggestion of a governing elite secretly protecting the abusers of children. Johnson was giving a validating wink to that hate-filled fringe, just as Donald Trump gave a friendly nod to QAnon or the Proud Boys. Johnson’s Savile move was classic Trump. For once a lie is out of the mouth of a national leader, it will be repeated by those whose salaries depend on his favour. Note the dispiriting interview with the culture secretary, Nadine Dorries, in which she refused to acknowledge the truth on Savile and Starmer, telling her interviewer “I only have your word for it”, as if provable facts were merely subjective opinions. Dorries was doing for Johnson what Kellyanne Conway did for Trump, creating a realm of “alternative facts”. This is the damage Johnson does. He did it a second time on Monday, randomly and without evidence suggesting that drug-taking was rife on the Labour frontbench. On Thursday, the UK Statistics Authority had to rebuke Johnson for falsely claiming crime was down when it is in fact up. The Savile smear was a demonstration of how low Johnson is prepared to go. He did not care that his remark would fuel ever greater distrust not merely in Starmer or Labour, but in the public sphere. Nor did he fear the corrosion that comes when a society cannot agree on a shared basis of evidence and truth, the slow death that is inflicted on democracy when each warring political tribe has its own “facts”. He did not and does not care about any of that. If he is to be driven from the temple, he will bring down the temple. He will scorch the earth. Conservative MPs now owe it to the country they claim to love to put aside their electoral calculations and remove this man, before he brings yet more ruin. Jonathan Freedland is a Guardian columnist