John Rentoul: A defining moment for... humble pie

Honesty proved an effective form of spin at Glenrothes and the momentum is with Labour

It just goes to show how difficult it is to write history while you are living through it. As well as losing my 50p bet on John McCain to win the US election, it may be that my early reaction to the bankruptcy of Lehman Brothers was wrong. That was the day, 15 September, that the credit crunch – previously a chewy abstraction rather than actually crunchy – suddenly made a loud cracking sound. I thought that it might be Gordon Brown's ERM, and not simply because of the coincidence that it was almost the same date – British membership of the European exchange rate mechanism was "suspended" on 16 September 1992.

It seemed that it would be the moment that Brown lost Labour's reputation for economic competence. It seemed implausible, on the face of it, that someone who made so much of prudence, yet who had borrowed in a boom so that there was little to fall back on in a bust, would benefit from the crisis. It seemed likely, on the other hand, that David Cameron would be the main beneficiary, even if he didn't strictly deserve it. After all, he had gone along with the borrowing, and was even committed to matching the Labour spending plans that he now derides as "irresponsible". But it isn't what oppositions do that matters in situations like this, as long as they avoid making fools of themselves. It is the Government and the Prime Minister on whom we focus.

This may yet be Brown's ERM, of course, albeit with a delayed reaction. Unlike the ERM, which had an immediate and catastrophic effect on the Major government's standing, the current crisis initially boosted Brown's popularity. Indeed, "Brown's bounce" ought to be a registered trademark of this paper. We used it first, reporting our ComRes poll of 21 September. Now Labour has won the Glenrothes by-election against expectations.

But I thought that it would be temporary, and that we ought to reserve the patent on "Brown's burst bubble" too. There is still an air of unreality about the recession, because job losses have not yet begun to bite and homes have not yet been repossessed in large numbers. I assumed that when the economic pain started to be felt, Brown would be unable to escape the blame. The famous media narrative, which sounds like Richard Dimbleby reading Jackanory somewhere up in the sky, would turn again. But that assumes that this is just a recession, a normal down of the up-down economic cycle. Labour would take the blame and the Conservatives would take the credit for the ensuing upturn. A bit like 1951, when Labour was punished for austerity and the Tories enjoyed 13 years of never having it so good.

What if, though, this is not "just a recession"? What if something more fundamental has changed? Some things are certainly different. To have nationalised a large chunk of the British banking sector is something that not even the Attlee government sought to do. And the Glenrothes result was so striking that it is possible that something big is happening. I do not believe that Labour campaign managers were engaged in expectations management when they said that they thought that the result would be close. I don't for a moment believe that Brown has abolished spin, but sometimes the best form of spin is to tell it straight, and I think that they thought that it would be close.

Of course, it is "just" a by-election. And, as Brian Brady, who has the advantage of having been there, reports on page 47, there were local factors: a strong Labour candidate, running as the opposition to the Salmond Narcissist Party on the local council and in the Scottish Parliament. Fighting a by-election as the government party in England against Cameron's Conservatives might be rather different.

But Labour's increased share of the vote on a high turnout requires an explanation. The last time the governing party did that was the Beaconsfield by-election in 1982 when the Tories won and one A C L Blair lost his deposit. And that was in the middle of the Falklands war, which really was a political game-changer.

At the very least, the momentum and the initiative, those indefinable but vital forces in politics, are with Brown. In the only opinion poll in Glenrothes, in September, Labour and the SNP were tied on 43 per cent; in all recent by-elections, Labour has lost ground between the last opinion poll and polling day. The feeling that the bottom has fallen out of the Gordon Brown market is no longer there. The threat from David Miliband has receded and, even if Labour MPs start to worry about holding their seats again, more than one Blairite minister has observed to me recently: "You can't fight someone with no one."

So that solves the mystery of why Alistair Darling, the Chancellor, said, two weeks before Lehman Brothers went bust, that the economic times were the worst for 60 years. Brown needs things to be really bad in order to convince us that this really is a paradigm shift.

I am a paradigm-shift sceptic, and not just because it is a trendy bit of pseudo-scientific jargon. Tony Blair claimed so many turning points and defining moments that he must have been spinning in high definition by the end.

Similarly with Barack Obama: his election is significant and a cause for celebration, but it will not sustain some of the higher expectations that have been placed upon it. Turnout, for example, was not a record – about the same as four years ago, perhaps a point or two higher.

Usually, defining moments and turning points are rhetorical devices rather than real events. Usually, continuity is more important than change. It is more likely that we are entering a recession rather than the end of capitalism as we know it. It is still more likely that Gordon Brown is heading for defeat at the next election than for a coalition with Nick Clegg.

But what do I know? Not only did I think that John McCain would win, I am the one who wrote the leading article for The Independent after 9/11 saying that it was very sad for the families of those killed but it wouldn't change anything. Doh.