Do you remember the centre ground, on which all political battles were fought? Well, where is the centre ground now?
Jeremy Corbyn says it has moved -- that today’s centre ground is not where it was twenty or thirty years ago, and Labour are now the political mainstream.
He may well be right. For more than thirty years, ever since the days when Ronald Reagan and Margaret Thatcher insisted that the less governments did, the better off we'd all be, the centre ground has been occupied by whoever broadly accepted that basic world view.
After Thatcher's death in 2013, Tony Blair said: 'I always thought my job was to build on some of the things she had done rather than reverse them.' David Cameron stood on the same bit of ground and claimed that he was the 'heir to Blair'. No wonder many voters concluded that there wasn't much difference between any of the main political parties.
And then along came Jeremy Corbyn, a man whose name had never, ever been found anywhere near the word 'mainstream'. 'We have left the status quo behind,' he told party activists in Brighton this week -- and few felt inclined to contradict him.
When the Cold War ended with the collapse of the Soviet empire, many people thought that the great ideological battle of the twentieth century -- capitalism versus socialism -- was over. The capitalist West had won.
But then came the Great Crash of 2008. Capitalism tottered. Banks were nationalised. Governments printed sackloads of money, and admitted they'd got it all wrong. Suddenly, all those politicians huddling on the centre ground, muttering about free markets and self-correcting mechanisms, sounded like cultists still insisting that they, and only they, had the answers.
Theresa May is still singing from that hymn book. No sooner had Mr Corbyn been cheered to the rafters by the Labour faithful than she was up on her feet at the Bank of England defending the old orthodoxy: free market economics, she said, are the 'only sustainable means of raising the living standards of everyone in a country.'
She's going to have a very tough job selling that message to the millions of people whose living standards have either stagnated or fallen since the financial crash ten long years ago.
Or to the Uber drivers and delivery couriers who work with no safety net between them and unemployment. Or to public sector workers who have seen their wages frozen and their numbers cut.
Yes, she says that she accepts that sometimes governments have to take action to fix 'broken markets'. And note the all-important qualifier in her otherwise ringing declaration : 'A free market economy, operating under the right rules and regulations, is the greatest agent of collective human progress ever created.'
Mr Corbyn has got the Tories rattled. It wasn't meant to be like this: how come a bearded Leftie (just for the record, I have nothing against bearded Lefties) is somehow more in tune with public opinion than the 'strong and stable' Conservatives?
It's not complicated: first the financial crash, and then the Brexit vote, have changed everything. Voters no longer behave according to the traditional nostrums of political life: that they don't like risk, and that they gravitate towards the centre. Not any more, they don't.
Even in Germany, the strongest and most stable of all Europe's leaders, Angela Merkel, failed to win as much support as she was hoping for in last weekend's election. Even in Germany, the home of consensus politics, the populist anti-immigration party, the AfD, won thirteen per cent of the vote.
According to the polling organisation YouGov, half of all voters generally identify with the centre ground, compared to just eleven per cent who say they are on the right and twelve per cent who say they are on the left. That's why Mr Corbyn is definitely on to something when he seeks to persuade us that Labour is the centre now. He has come a long way, including learning how to look and sound like someone with claims to be a prime minister -- since being elected as party leader two years ago.
Perhaps his greatest achievement in Brighton was to hide the deep Brexit divide that threatens Labour every bit as much as it threatens the Tories. But he also, shamefully, continued to ignore the existence of the ugly underbelly of the Corbynista bandwagon -- the misogynistic, and sometimes anti-Semitic, bullying that is too often targeted at anyone regarded as not sufficiently loyal to the cause.
And as for his apparent tolerance of the frankly grotesque personality cult that he seems tacitly to accept -- 'Oh, Jeremy Corbyn' indeed. It seems that this famously modest man rather likes the limelight after all.
Will Mrs May manage to hold her party together and paper over the cracks at their conference in Manchester next week? With her record -- and with Boris ('The Joker') Johnson in full mischief-making mood -- I wouldn't take any bets. For now, it's Mr Corbyn who has the wind in his sails.