In the statement that accompanied his resignation as transport minister, Jo Johnson accused his own government of a “failure of British statecraft on a scale unseen since the Suez crisis”. He is wrong. Brexit is many multiples more serious than the Suez debacle of 1956 and the consequences of a bad Brexit will be felt for far longer than was Sir Anthony Eden’s misadventure in the Middle East. That cost him the premiership, but the humbling retreat from the desert taught his country and his successors at Number 10 a valuable and necessarily brutal lesson about the limits of Britain’s post-imperial power. Suez did no lasting damage to Britain; arguably, that fiasco did this country a favour by burning away illusions about its place in the world. Nor was there enduring harm to the Conservative party. The Tories quickly ditched Eden and went on, under Harold Macmillan, to win a landslide election victory less than three years later.

If the economic blowback is nasty, the Tory party will not be able to repeat its post-Suez trick

Suez swiftly faded from controversy and slipped into the history books; Britain and its Tories will be living with the consequences of a bad Brexit for years – probably wisest to make that decades – to come. If the economic blowback is nasty, the Tory party will not be able to repeat its post-Suez trick. It will not induce forgiveness and forgetfulness about a terrible Brexit simply by installing a new face at Number 10.

Politics is often a case not of how you play the game, but how you place the blame. No one does this more assiduously and mendaciously than the Brexiters. Their game is approaching its climax and we can smell their fear that it is going to end very badly. This is why their fiercest energies are now directed to diverting culpability on to anyone’s shoulders but their own.

The person they have allotted to play the principal scapegoat is Theresa May. The prime minister will not be alone on their bogus charge list. They will finger others who supposedly sabotaged a beautiful idea, a cast that will include quisling civil servants, the treacherous Treasury, recalcitrant Remoaners, meddling judges and bullies in Brussels. They will all have roles in the self-exculpating blame game the Brexiters plan to play, but it is the prime minister who is being assigned the part of chief villain. Once, when she was foolishly following their script by painting herself into their “red lines”, they adored her. Now she will be Theresa the betrayer.

She has to be, for otherwise the betrayers of Britain would be the Brexiters themselves. Human beings are, by and large, reluctant to admit error and politicians struggle more than most of us. Confession of fault comes even more grudgingly when the mistake is as epic as Brexit. If you have founded a world view on a folly, if you have staked an entire career on the idea that quitting the European Union is a bright idea, then you would have to be exceptionally honest with yourself to confess that it has been a catastrophic mistake. The Brexiters are not capable of being honest with themselves – or anyone else. Since their self-conceit will not allow them to concede that the fault is in Brexit itself and the people who promoted it, blame must therefore be assigned elsewhere. There was a dream Brexit to be had – this will be their cry – if only it had not been chucked away in the chambers of Brussels. Had Mrs May been a smarter, tougher negotiator, Britain would now be looking at a sun-dappled future, rather than being asked to accept a dire deal that leaves virtually no one satisfied and nearly everyone unhappy.

The Brexiters will protest to the end of days that there was nothing inherently wrong with their concept

In this, the Brexiters remind me of the Marxists during the days of the Soviet Union and the excuses they would trot out to explain why the USSR had not turned out to be the workers’ paradise promised by old Karl’s theories. When forced to acknowledge that all the regimes that have governed in the name of Marxism had been a disaster, they would insist that this did not prove that communism was a fatally flawed idea, just that it had never been given a proper try. Just so with the Brexiters. They will protest to the end of days that there was nothing inherently wrong with their concept – it was the execution that was to blame.

So it is important for the rest of us to be clear why we have wound up in a position where Mrs May is attacked by both the Johnson brothers, the Remain-supporting younger one who has quit the government to campaign for another referendum, and the Brexiter older one who flounced from her cabinet in the summer. Mrs May has not arrived in this place of peril – for both her premiership and her country – because she is an especially dreadful negotiator. It is not true to say that there was a brilliant deal available if only she had tried a bit harder.

Mrs May is in an impossible position, because a good Brexit never existed outside the glib fantasies of its proponents. There has never been a deal available that would allow the United Kingdom to continue to enjoy all the many benefits of its partnership with the European Union, as the Brexiters once promised, from the outside. As I’ve remarked before, any deal negotiated by any prime minister was bound to be suboptimal, because there are no terms more favourable to Britain than those that it currently enjoys as a member of the EU. There never was some tremendous bargain there to be struck if only Mrs May had had the wit to spot it. From the start, she has been choosing between varieties of the inferior. And where she has made mistakes, they have flowed not from betraying the hard Brexiters but from doing their bidding and seeking to appease them.

It is now nearly 30 months since the referendum, with fewer than five to go before Britain is due to leave. If there were some smart solution to Brexit, we are entitled to wonder why the Brexiters have never revealed it to the rest of us. They have been florid in their denunciations of Mrs May’s ideas without once producing a plan of their own that passes the most basic tests of viability. Michael Gove, purportedly the cleverest of their number, has been reduced to arguing that the cabinet should swallow whatever terms Mrs May can cobble together in the hope of having another go at some unspecified date in the future.

If there were a blindingly superior negotiating strategy, and the secret of it was known to Boris Johnson or to David Davis, you might think they would have shared it with the rest of the cabinet when one held the great office of foreign secretary and the other was in the influential role of Brexit secretary. Those positions are now held by Jeremy Hunt, a self-proclaimed convert to Brexit, and Dominic Raab, a protege of Mr Davis and always a believer. They have done no better than their predecessors at illuminating the path to El Dorado.

Mrs May could have been 10 times more skilled at negotiating and Britain would very likely be in much the same place

A clue to why they have failed was dropped in the past few days by Mr Raab. He is not a stupid man – the opposite, in fact. But like many of his fellow Brexiters, he can be astonishingly ignorant. He told a tech industry conference that he had only recently grasped how much of Britain’s commerce is dependent on free flows across the Channel between Dover and Calais. Britain is an island? No shit, Sherlock. This follows the admission by Karen Bradley that, prior to becoming Northern Ireland secretary, she “didn’t understand” that the territory had sectarian divisions, the most elementary fact about its politics. This had you wondering how Ms Bradley managed to get into her late 40s, and a chair in the cabinet, without ever watching a news bulletin or reading a book. It was from such boggling political, geographical and economic illiteracy that sprang the fatal fantasies that Brexit would be a piece of cherry-topped cake.

Mrs May could have been 10 times more skilled at negotiating and Britain would very likely be in much the same place as it is now. The younger Johnson characterises it as a choice “between two deeply unattractive outcomes – vassalage and chaos”. At best, Mrs May will present a deal that is humiliatingly worse than the terms we currently enjoy as members of the EU. At worst, Britain will be invited to take the nightmare road that leads over a cliff-edge. This wretched choice will be offered by Mrs May not because she is the most hapless negotiator ever to inhabit Number 10; it is because a happy ending to this story was never available.

The problem with Brexit is not Theresa May. The problem with Brexit is Brexit.

• Andrew Rawnsley is an Observer columnist