As Labour crumpled, Cameron promised to “bring our country together”. If you think he brings balm, you probably believed Margaret Thatcher really meant to rule like St Francis with her prayer, “Where there is discord may we bring harmony”. Ahead lies fracture and class division.

Discord starts now, as Cameron plunges Britain into two pointlessly damaging years of strife over Europe. When he returns from bogus “renegotiations”, a host of his rebellious backbenchers will stampede for the exit and Cameron may lack the heft to gain the necessary concessions. Scotland will be gone, our UN seat improbable, the sun setting on a shrunken little England.

The £12bn cuts to benefits are so frightening that Cameron refused to define them in the election

On this unhappy day let’s just list what Cameron will do, as his ministers swore yesterday to “absolutely stick to our manifesto commitments”. The Human Rights Act will be gone, remaining social housing sold off with the NHS propelled into the private sector. The press will be rewarded for their filthy North Korean election coverage. Forget Leveson, Murdoch can expect bounty and the savage pruning of the BBC he always demanded.

Epic cuts will tear into public services, the state shrinking year by year. The £12bn cuts to benefits are so frightening that Cameron refused to define them in the election. Inequality will take off, along with child poverty: Office for National Statistics figures reflecting the social effect of the last five years will conveniently only emerge in June – and will be a harbinger of far worse to come.

The world of work, Osborne’s “jobs miracle”, will see more CBI-favoured “flexibility” of zero hours and temping. Here are Institute for Fiscal Studies predictions on the effect of Osborne’s plans: 1.3m public jobs will be gone by 2019, and self employment (average earnings £10,000 a year) will overtake public sector jobs by 2018. By then public sector pay will fall 8% behind private pay – while top tax and death duties are cut for the highest earners.

The future is dark. In England and Wales the people swung to the right, with Labour barely improving on its Gordon Brown vote. Is Cameron’s scorched-earth social and institutional destruction of the public realm really what the people voted for?

Impossible to tell. The polls were so outrageously wrong that any future polling trying to find to out why will be as useless as the originals. We just don’t know, so we are left to guess what people thought.

Should we have known the way the wind was blowing? By the pricking of our thumbs, many of us Guardian commentators felt in our travels that we didn’t see Labour leaping over its gigantic obstacles.

“Maxing out the credit card”, refusing to give the keys back to “those who crashed the economy” – those clever Tory lies resonated strongly. Nor did Miliband connect on the doorstep. But how can you set your anecdotes against the thundering unanimity of the polls? World-class pollsters such as Nate Silver swore the polls were rock-solid within a small margin of error. That drumbeat was so loud that we set aside any unease. Next time, we won’t.

After the raw agony, a long dark night of the soul awaits Labour – and that began before the chimes at midnight. Who will lead them down which fork in the road? March back to the centre ground! No, copy the Scots and Greens! The field is wide open.

But here’s one essential. With five years ahead, Labour must not rush to any wrong judgments. Let dust settle, let misery and anger subside, allow time for rational assessment of the way out of this abyss. Take the pulse of a new Cameron government at risk of hubris and reckless triumphalism.

Let Harriet Harman act as interim leader for six months to give the party time to recover and regroup, just as Margaret Beckett held the fort after John Smith’s death. The Tories gained greatly by Michael Howard agreeing to stay on long enough in 2005 to allow Cameron, the unexpected interloper, to break through. Labour too has talents worth testing beyond the obvious frontrunners.

Before the party embarks on recriminations, it should remember what it knew in 2010. The Everest to climb was virtually impossible: governments almost always win a second term. Labour’s reputation for economic competence was unjustly poleaxed by the crash, and the explanation was far too complex for election messaging.

Some who want a new leader installed quickly say the lie that overspending by Labour caused the crash went unrefuted when Labour spent too long in a navel-gazing leadership contest. But almost every government around the world at the wheel during the crash was brutally ejected. It’s no reason why Labour should dash for a new leader now.

There’s no evidence David would have fared any better – they’d soon have said he was the wrong brother too

A leader’s fall always has Shakespearean echoes, and the Miliband brothers’ drama has epic tragic elements. Today Ed stood at the cenotaph like a man at his own funeral. Decent, well-liked, his warm intelligence in private rarely showed itself in his awkward public appearances. He never learned those essential thespian skills for the television age: no use his friends comparing him to Attlee.

Davidites may gloat, but there’s no evidence he would have fared any better. He had different strengths and defects, another north London geek they’d soon have said was the wrong brother too. Unkind, today, to pick over the fallen leader’s failings – but here’s one lesson. He was often praised for his remarkable resilience in the face of torrential mockery and abuse. How could he take such personal humiliation?

The brutal answer is that he shouldn’t have done. Both he and Gordon Brown became millstones around their party’s neck and both should have stood down with grace in the year before the election. They could have earned genuine respect by handing over to anyone who might win crucial extra votes. At the hustings for the next leader, each candidate should pledge to step down if they, too, become a drag anchor, not an asset.

Every time Labour fails, the key issue is not their ejected MPs nor the great Westminster game, but the hardship imposed on the low-paid and hard-pressed. Every Tory government makes the rich richer and the poor poorer, draining public services dry.

Ignore Cameron’s urbane manner, he is driven by a deep anti-state ideology that will leave the welfare state and the public realm unrecognisable in five years. That is what Labour’s failure means.