Conviction often has its own contagious energy. When Dominic Cummings was briefly director of strategy for the then party leader, Iain Duncan Smith, in 2002, there were occasional lunches for journalists at what was then still called Conservative Central Office in Smith Square. Cummings would sit at one end of the table in open-necked shirt and jeans, bellowing about the inadequacy of the Conservative party; while IDS, in pinstripe suit, sat meekly, head bowed, at the other end, like a deeply unhappy vicar being berated by an evangelical member of the parish council. It was easy to forget that, technically at least, Duncan Smith was the one in charge.

Even now, after Boris Johnson’s disastrous week – capped by the dramatic resignation of Amber Rudd last night – many are still mesmerised by Cummings and his cunning plans. Not unreasonably, they recall his choreography of Vote Leave’s victory in 2016. Less reasonably, they persuade themselves that the present mayhem is all a necessary prelude to eventual glory, citing the Leninist maxim that “worse is better”.

As she now admits, this government is not preparing for a Brexit deal at all. No deal is now its highest priority

Look at the polls, they say. The Tories are ahead – by 14 points, according to the latest Sunday Times/YouGov survey. Ergo – according to the No 10 faithful (let us call them Dominicans) – Cummings is right to contrast the prevailing wisdom in the political and media class (which he describes with the shorthand “SW1”) with the views of the electorate beyond the Westminster village.

This much, I suspect, is true. The voters have fallen out of love, for now, with Jeremy Corbyn (though the 2017 general election is a warning against dismissing the Labour leader too glibly). They are also heartily sick of Brexit, sick of the whole argument, sick of the real world complexity of a process they were assured in 2016 would be thrillingly easy.

After three years of dither and delay, it is not hard to imagine a measure of public sympathy with Johnson’s contempt for convention: his suspension of parliament, his purges, even his declared readiness to break the law. We are undoubtedly living through a populist moment, marked by a high degree of frustration with representative democracy, its flummery and its procrastinations.

What I do not think is that this frustration yet amounts to a blank cheque, or anything like adulation for the prime minister. Voters want Brexit sorted (whatever that means); but I am much less convinced that they are longing to make Johnson galactic emperor and to give Cummings the right to wear in public the Darth Vader helmet he surely already has in his desk drawer.

Prime minister Boris Johnson. Photograph: Murdo MacLeod/The Guardian

Fixated by their tactical objectives, the prime minister and his right-hand man are courting strategic disaster. In less than a fortnight, Johnson has managed to expel or drive away just about every senior Conservative MP who had a claim to being described as humane, moderate or decent. Ken Clarke, Rory Stewart, Oliver Letwin, Justine Greening, Nicholas Soames. You may not like all or any of these Tories, but I hope you’d agree that getting rid of them has not exactly helped those who still assert that the Conservatives are a mainstream, “one nation” party.

Johnson’s own brother Jo was so appalled by the expulsion of the 21 MPs that he is leaving politics altogether. As Rudd told the BBC’s Andrew Marr Show , all this is “a big symbol”. She herself was once considered by many in David Cameron’s circle as the moderniser best placed to succeed him.

Although her majority in Hastings is tiny, she was often touted as the natural replacement for Theresa May – a prospect that receded sharply after her resignation from the Home Office over the Windrush scandal. Although she backed Jeremy Hunt in the leadership contest, she continued to believe that Johnson could be steered away from the abrasiveness, recklessness and nativism of the more extreme Brexiteers.

And she was wrong. As Rudd now admits, this government is not really preparing for a Brexit deal at all: its mission is to leave the EU on 31 October by all and any means necessary. The no-deal outcome that Johnson promised in June was “a million to one against” is now his highest priority.

In driving out Rudd and all the others, the prime minister has managed to make Corbyn’s Labour look like a broad church: quite a feat. Stella Creasy, Yvette Cooper and Jess Phillips may not be on the frontbench, but they have not been purged (not yet, anyway).

The rich irony is that Johnson himself used to be – or at least behaved as if he were – exactly the sort of Conservative which he is now expelling. He was the so-called “Heineken Tory”, who could reach the parts of the electorate other members of his party could not. It was routine for those on the left to say that they hated most Conservatives with a passion but could still imagine having a pint with Boris.

The Tories have always desperately needed such figures: those who humanised the party’s tough, technocratic face and acted as guarantors of its intentions, at least to a sufficiency of voters. Just as Labour always requires a cohort of protagonists who exude competence as well as compassion, so the Tories cannot survive without a core of ambassadors who do not look as though they list “implementing austerity at the weekend” as their hobby in Who’s Who. And now they’re all gone – most of them, anyway.

Who knows if they’ll be back? Meanwhile, Johnson is wrecking the Conservative party at astonishing speed, turning it into a single-issue campaign group with no soul or purpose beyond the completion of his Brexit dream. But why should he care? As Cummings would doubtless say, he had to destroy the Tory party in order to save it.

• Matthew d’Ancona is a Guardian columnist