“A new dawn has broken, has it not?” asked a triumphant Tony Blair on that May morning in 1997. Indeed it had. But oh no it hadn’t, say those now controlling Labour. History is fluid, a prism shifting the light of now, so some days New Labour’s record shimmers, other days it’s clouded by all the opportunities missed.

Twenty years ago in the throes of that election campaign, Blair and Gordon Brown were terrified by the prospect of a 1992 reprise. That shock result was seared into their souls, convincing them that England was so ineradicably conservative that Labour could win only by stealth. History conveys the illusion of inevitability: how absurd now to think that they ever feared losing to that rabble of Tories killing each other over Europe, mired in sex and money sleaze, having never recovered from crashing out of the exchange rate mechanism. Of course Labour was bound to sweep to its greatest ever victory on a swing of over 10%.

That shock 1992 result convinced them that England is so ineradicably conservative, Labour could win only by stealth

New Dawn? is an exhibition at the People’s History Museum, in Manchester. Curated by Prof Steven Fielding, it will rack the heart of Labour people, wherever they stand now. In a lifetime on the left there have been pitifully few glory days: I had the teenage joy of 1964 after “13 years of Tory misrule”, but the shock loss of 1970 was a salutary lesson. Then came 1979, 1983, 1987, 1992: crushing defeats, and a wretched 18 years before 1997’s euphoric dawn. I remember talking to crowds outside Downing Street, people who had jumped into their cars and driven through the night from far-flung corners just to be there that morning, intoxicated with unaccustomed hope.

Some got their disillusion in early, refusing to celebrate that day, the ones who now hurl “Blairite” at any who praise those unique three wins. Life on the British left is predestined disappointment. Even for those not impatiently Utopian, no Labour government can or will ever do enough.

At a museum debate last week, I rattled through 50 Labour achievements, a random selection including 3,500 Sure Starts, peace in Northern Ireland, 85,000 more nurses, the minimum wage, devolution, doubled school funding per pupil, a million pensioners and as many children out of poverty, foxhunting banned, civil partnerships created, overseas aid doubled, free nurseries – and a plenitude more. That timid little pledge card in 1997 blossomed into vastly more. Snatching £5bn from privatised utilities to spend on cutting youth unemployment was remarkably radical.

Regrets? Labour has many, with Iraq the worst. At home the fear that gripped Blair and Brown stopped them challenging Thatcher’s pervasive political legacy. They did much good but stealthily, never shifting the public discourse. Tax was always a “burden”, never the price for civilisation – to be cut, not raised, even as top pay shot through the roof: promising Scandinavian services on US tax rates was a free-lunch miasma. Public services were thrashed with mostly useless “reforms” and outsourcing, to prove New Labourism.

Facebook Twitter Pinterest ‘Labour’s tax bombshell threat did for Kinnock in 1992.’ Photograph: The Conservative party archive/Getty Images

Failing to breathe pride in the public realm into the national psyche allowed the returning Tories to pull it up by the roots. Sure Starts are all but gone, NHS and social care starved, schools cut, and benefits massacred, with inequality destined to soar by 2020 as it did in Thatcher’s 1980s. Labour shares the blame for Brexit, Blair and Brown – cowed by the Eurosceptic press – never promoting the European idea, or easing immigration’s problems. If only Blair had followed his instinct on a fair voting system, he might indeed have secured the 21st century for the left.

How easily David Cameron and Theresa May have grubbed up Labour’s legacy, as the deal was never sealed because Blair never thought conservative England could be persuaded, only lulled into acquiescence – by talking tough and redistributing quietly, without leaving a nicer, kinder country.

On that morning in 1997 only a Cassandra could have predicted where Labour would find itself today, back in a Michael Foot wilderness. Ben Page of Ipsos Mori tells me that Labour is where it was in 1985. It may be optimistic to assume the pendulum always swings back in the end, with some fearing that these may be Labour’s end of days. At 18 points behind in the polls, 55% seeing May as best leader, Jeremy Corbyn only on an abysmal 18%, Labour has no guaranteed recovery. And the party is paralysed by a membership convinced against all precedent that a leader sunk so low in public esteem can still revive: a grim stasis of despair has descended, a dull ache with no escape, as yet.

We cling to a faith that democracy always rights itself. But history is discouraging: the Tories usually hold power until, once in a while, they exhaust themselves, blunder or implode. In 1945 they were running on empty. In 1964 Alec Douglas-Home in plus-fours was as fatally the wrong man to lead as Corbyn is now, both parodies of what the public most disdains about their parties. Ted Heath lost his grip over his three-day week. John Major fell when his party lost its instinct for power. Brexit could bring May down, or neglected services, or falling living standards. But don’t rely on it. As 1992 warns, a failing Tory government is a necessary prerequisite for a Labour victory, though never a sufficient one.

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In 1997 Blair was famously called a butler tiptoeing across a polished floor with a Ming vase, terrified of any false step. “Labour’s tax bombshell” threat did for Kinnock in 1992, so “prudence” was the watchword this time. No spending, none, for two years, no tax rises, only iron discipline – and yet a convincing message of hope, another election-winning necessity. “Things can only get better” was optimistic, but not wildly.

At this exhibition in Manchester, Labour people confronting the election images can only look back on 1997 in sadness, wherever they stand on the party’s spectrum. Everyone will choose their preferred lesson: Corbynites will shake a fist and ignore all it took to get that Ming vase over the line. Others will ask what more Labour could have done to secure its legacy. History will be kinder to Blair, thinks Fielding, as his three victories outlive old ideological disputes. Look how Clement Attlee has become a hero, yet the Bevanites despised and harassed him every step of the way for his moderation, as John Bew’s biography chronicles.

History bends and flexes as we pick angles to suit present arguments. In straits this dire, Labour should contemplate 1997, and ponder whether such days will ever come again.