In retrospect, the centre of British politics came apart during the 2000s. The constitution rotted. Turnout fell. The SNP took power as a minority government in Edinburgh, and bided its time. After Iraq, voters stopped believing much they were told about foreign policy. When the 2008 crash came, the party leaderships could not explain why it happened, or see what it might generationally unravel. Instead they used overblown partisan rhetoric to score small electoral points. None admitted that whichever party won in 2010 they would all act much the same way to reduce the budget deficit, while trusting the Bank of England to use whatever monetary fixes available to reboot an economy that no longer worked.

When Scottish voters threatened to topple the Union, the coalition and opposition party leaders were shocked into action, their deceit that it was for Scottish voters alone to choose on independence without Westminster’s intervention shattered. Scuttling up to Scotland, David Cameron, Ed Miliband and Nick Clegg vowed to rewrite the UK constitution to Scotland’s benefit, as if the Union’s governance were not a matter that concerned any other part of it, or required contested discussion in parliament.

The 2015 general election was the twilight moment for liberal, centrist politics. The Conservatives won that election because they crept just enough outside the old consensus: in attack, exploiting the English problem; in defence, minimising Ukip defections from the party by the EU referendum promise. Labour, by contrast, was clueless about the forces at work, misreading Ukip’s support and the Liberal Democrats’ collapse, and entirely blindsided by the SNP.

Jeremy Corbyn’s opportunity came because Labour’s task appeared hopeless over one parliament. Despairing, enough members and three-pound voters thought they might as well claim Labour back from the grind of figuring out what recalibrations were required to dislodge the Conservatives in Swindon. Corbyn’s opponents neglected to exploit his Euroscepticism, apparently unaware that the EU referendum was about to dominate politics. None of them warned that Corbyn’s long history of association with anti-Semites would open a nightmare. Indeed, few Corbyn critics, even now, are willing to consider why 2,000 years of history means anti-Semitism is more than another type of racism, or reconsider their assumption that (albeit regrettably) an anti-Semitic Labour Party has to be a price worth paying to stop the Conservatives.

The electoral necessity for the Conservatives of Boris Johnson was generated by the struggle over whether Brexit happens at all. For all her toil, Theresa May assumed Brexit could occur without a further fight. But she had little chance of translating the non-Tory part of the Leave coalition into Conservative voters without money her chancellor would not spend. At Westminster she failed to perceive that Remainer resistance ruled out ratifying a withdrawal agreement that did not command much support from Leave MPs.

Confronted with May’s wreckage, Johnson’s pagan energy, directed above all else at historical fame, became all the Conservatives had left. It may loftily detach him from everyday concerns. It sets few, if any, internal limits on what he will do or tolerate to win. But it also means he courts jeopardy, and without his political risk-taking, the Conservative Party would be finished.

Liberal centrists bemoaning the unpalatable choice between Johnson and Corbyn miss their own culpability for Johnson’s ascendancy. If the Conservatives win by turning Labour seats in the Midlands, the north and Wales, it will not just be because long-time Labour voters detest Corbyn. They also don’t much care for those Remainers in the Labour Party who have loudly told them that their vote in 2016 was a moral and cognitive failure and their support for Labour in 2017 dispensable. If Labour, nonetheless, get close it will be down to a generation of Labour voters the Corbyn project inspired.

Nor can the obvious ethical issues around Johnson’s character be conflated with the political direction in which he has taken the Conservatives. Leaving the EU in an orderly way is extreme only if judged by the political spectrum of British politics Tony Blair shaped, and entirely independently of the political predicaments the EU creates. Remainer MPs deemed May’s withdrawal agreement a “hard right” Brexit when for the medium term it near guaranteed staying in the customs union. If they are now horrified at the ERG members sitting high in Johnson’s cabinet, they might reflect that they chose to treat the ERG’s defeat over both withdrawal agreements as the first instalment of a bigger victory. They might also absorb that, despite the ERG, Johnson is moving the Tories economically leftwards.

Liberal centrists have been as uncompromising for the past three years as anyone. Those who would stop Brexit have pursued victory without any notion of how Britain’s membership could be politically stabilised if they won. For all their claim to superior competence, they also lack political judgement. Johnson’s gamble on renegotiating created not only the last chance the Conservatives have to achieve Brexit, but simultaneously a path to the second referendum they craved. Finally, they had a Leave option that could credibly be pitted against Remain. But instead of pledging such a referendum, the Lib Dems ploughed on with Revoke and Labour’s Remainers have stuck with the obvious problems of a Leave referendum option that virtually no one at Westminster who supports Leave would politically own.

Political choices are always hard, and in this election they are painful. But liberal centrists who helped make them this way cannot demand back the political privileges they threw away.