What George Orwell said of left-wing intellectuals now applies to Boris Johnson and his ministers: so much of what they propose is a ‘playing with fire by people who don't even know that fire is hot’.

They may suspend Parliament and crash us out of the EU on 31 October or crash us out in the middle of an election campaign. Understandably, all the talk is of the threat to the conventions of democratic life. Yet if Johnson does not buckle, the autumn will not just bring a constitutional crisis but an economic and social crisis.

No one knows how bad crashing out will be because no country has been stupid enough to tear up its main trading relationships without having an alternative in place. But it is not hard to imagine panic as the pound falls and the threat of job losses, food and medical shortages grows. The realities of Brexit, for so long an argument dominated by fantasists, will confront the British for the first time, and the next election will have the atmosphere of a revolutionary crisis.

The Tory right think they can get away with tearing up constitutional norms because Jeremy Corbyn’s unpopularity gives them the freedom to do as they please. Their assumption, that he cannot become prime minister, allows them to treat Parliament with contempt, without worrying that they are providing a precedent a radical left government would be free to imitate.

No one can predict with certainty if they are deluding themselves (again) and will live to regret their recklessness. But we can say that a second assumption is starting to fall apart. Johnson’s strategy is to unite the Conservative and Brexit party votes and face down a divided opposition. Yet opposition divisions are healing with remarkable speed.

On 15 August, the attempt to build an effective remain force will begin when the Liberal Democrats, Greens and Plaid Cymru agree a non-aggression pact in 30 constituencies. They will back one candidate in each seat who will stand as X Liberal Democrat (Unite to Remain) or Y Green (Unite to Remain) and so on.

My understanding is that the easy decisions are close to being taken. There’s agreement that sitting MPs should be given a free run, and on the names of candidates for obvious target seats. The Greens were far ahead of the Liberal Democrats in the Isle of Wight in the 2017 election, for example, and will provide the sole remain candidate in the constituency next time.

A second tranche of 30 or so constituencies will be settled on 22 August. As the parties move down the list of target seats, the task becomes harder. In each constituency they are asking activists to step aside for a rival, a hard concession for many to make.

Nevertheless, the scale of the national crisis and the almost universally hostile reaction from remain voters to the Greens, Change, Lib Dems and nationalists splitting the vote in the May European elections is concentrating minds. All three parties are close to deciding who should stand in every Welsh constituency except Ceredigion by Cardigan Bay, a Lib Dem/Plaid marginal that the Tories have no chance of winning.

On occasion, it can suit parties to share the load. If you just looked at the 2017 election results, the Liberal Democrats would appear the obvious party to fight all six of the Cornish seats. But if they went for every seat they might disperse their resources, and win just one. The plan is for the Lib Dems to target four constituencies in the county, and hope to win three, and leave the Greens to fight the remaining two – probably Truro, Newquay and Falmouth and Camborne and Redruth. Green politicians know how Corbyn and his supporters operate. Even though the party has built support mainly in Labour seats, it will avoid inevitable accusations that it is aiding the Tories, or worse, turning “centrist”, by fighting prominent Conservatives: most notably Amber Rudd in Hastings and Rye and, perhaps, Maria Caulfield in Lewes.

The final meeting on 6 September, in the week Parliament returns, will be the most important. Candidates for a final tranche of about 40 seats will be chosen. It will also be the deadline for independent MPs to decide what they want to do. The Commons has 16 independents already, and could see more by next month. If they want support, they can join one of the Remain parties – Sarah Wollaston, the former Tory MP, and Angela Smith, ex-Labour, will join the Lib Dems next month. They can run unopposed as independents, if they can reach agreements with remain parties, or perhaps a new umbrella party could be created to accommodate them. After 6 September, all deals are off.

To generate publicity and raise morale, the alliance is talking about targeting high profile Brexiters: Jacob Rees-Mogg and, possibly, Jeremy Corbyn. The local elections showed the Liberal Democrats in Mogg’s Somerset North East could win if they can squeeze the Labour vote.

In Islington North, the argument about running a unity candidate has yet to be resolved. I cannot get confirmation, but my best guess is they will choose Caroline Russell, a popular and impressive Green councillor, who has been the sole opposition voice in what is otherwise a one-party Labour state.

That agreements of any kind are being reached between rivals is testament to the willingness of Jo Swinson and Caroline Lucas to dispense with tribalism in a national crisis, and to the work of Heidi Allen’s Unite to Remain. Its staff have analysed all available data from polls, elections results and canvassing returns. Its most optimistic assumption, based on Nigel Farage splitting the right-wing vote, suggests that 200 seats could be vulnerable to a remain challenge. Allen and her backers have also provided financial incentives to cooperate. Like so many others, remain donors want a common front. If the parties can agree on a single candidate in a seat, Unite to Remain will finance him or her directly. If they can’t, they don’t get a penny.

When the histories of the Brexit debacle are written, I am sure they will concentrate on the crucial failure of the Labour party to mount an effective opposition. It already haunts the Unite to Remain campaign. It cannot enter into formal pacts with pro-European Labour MPs, because Labour at national level will not offer concessions in return. In any case, Corbyn is still a pro-Brexit Labour leader, and his supporters give every appearance of hating Jo Swinson more that they hate Boris Johnson.

I am told that Labour MPs who have fought Brexit will face only paper challengers. There will be a Liberal Democrat on the ballot paper, for instance, in Ben Bradshaw’s Exeter and Peter Kyle’s Hove but campaigning efforts will be directed elsewhere.

That may not be enough. In three- or four-party contests, and with first-past-the-post system going haywire, a few thousand or even a few hundred votes to a small party may let Conservatives in through the middle.

More generally, I cannot see how the Brexit right can can be beaten if the main opposition party does not dispense with far-left sectarianism and declare itself willing to build the widest possible alliance against Johnson and Farage.

But then I am a habitual pessimist and, for once, would enjoy nothing more than being proved wrong.