John Rentoul: The Prime Minister will pay a high price for his dithering

In the space of a week Gordon Brown has gone from sure-footed statesman to nervous wreck

I t is 1990 all over again. As today's A-level Politics students were born after the fall of Margaret Thatcher, a short revision guide may be needed. John Major, a new pragmatic Prime Minister, had taken over from the hated former leader, and had proved surprisingly popular. His calm style was a welcome change from the strident certainties of his predecessor. As George Osborne, the shadow Chancellor, pointed out last week, Major enjoyed a much bigger "bounce" in his party's opinion-poll ratings than did Gordon Brown. That does not prove what Osborne wants it to, though. He implies that Brown now is less popular than Major then; what it really shows is that Thatcher was more hated then than Tony Blair was three months ago. I am sure this is welcome news in Connaught Square, as Blair waits to be invited to tea at No 10 by some Tory prime minister in the distant future.

The point is that, in 1990, the Conservatives were transformed from a party facing certain defeat – at the hands of Neil Kinnock, remember – to one that held a narrow opinion-poll lead over their opponents. Major, keen to win his own mandate, thought about calling an election. His deliberations were not as artificially puffed up in the media as Brown's were, but there was some speculation about a "khaki election" after the success of the first Gulf War in February 1991. But Kinnock fought back. With a summer campaign, "Opportunity Britain", Labour took a small lead in the opinion polls. For 18 months, the Prime Minister looked for a chance to go to the country, and every time it started to look possible, the Opposition rallied and the election date receded again. In the end, Major was forced to go for almost the full five years, finally getting out his soapbox in April 1992.

One of the instant myths that has sprung up in the past few days is that the opinion polls now are particularly volatile. They are not. Just as in the early Nineties, the trends are clear. The figures for each of the parties vary from poll to poll, usually by two or three percentage points from the average. The lead – currently a Labour lead – varies more sharply, being the difference between two numbers, each subject to random variation. But the underlying picture is fairly stable. Labour enjoyed a small post-Bournemouth bounce, after Brown's 89 sentences beginning with "And" that some people called a conference speech. Then the Conservatives enjoyed a post-Blackpool bounce – largely at the expense of the Liberal Democrats – that cut the Labour lead to an average of two points. My guess is that the polls will settle back towards the pre-conference averages.

That suggests a Labour lead of around five points. To which I then apply the "under the table" adjustment. So called because I was under Peter Kellner's table when the 1992 BBC election night programme went on air. I was trying to plug in his laptop power cable, which had fallen out at the crucial moment when the exit poll forecast changed four minutes before the titles rolled. The screen behind David Dimbleby changed from Kinnock's face on a red background to Major's face on a blue background and the programme editor was screaming at the boffins – of whom I was one – to explain where the small Labour lead in all the opinion polls and in the early exit poll returns had gone. In that election, and the three elections since, the opinion polls in the campaign have overstated Labour's share of the vote by an average of five points. That would wipe out Labour's current lead and could pitch Brown into a hung parliament.

So it was not safe for the Prime Minister to call an election. Brown considered the option more seriously than I thought he would but, just as Kinnock did in 1991, Cameron and Osborne did enough last week to postpone the election. Cameron's speech was low on content, and Osborne's sums don't add up, but the impression given was favourable.

Now Brown has to count the cost of his indecision. He is prepared to live with the embarrassment of the "bottler Brown" headlines. He is tough enough to get through Cameron's public-school teasing at Prime Minister's Questions on Wednesday. It is true, as the wise heads of Westminster say, that such froth will blow off the media cappuccino in a few days.

But more lasting damage has been done to Brown's reputation. The most effective sound bite delivered at last week's Tory conference was William Hague's: "Gordon Brown is not a conviction politician. He is a calculation politician." What was extraordinary was that Brown's advisers confirmed this by telling journalists that their man would make the decision about election timing after studying the opinion polls at Chequers. He would not be deciding what was in the best interest of the country, but where his party-political interest lay.

A Cameron adviser told me that he saw the headline, "Another day another photo opportunity", on Channel Four News on Friday lunchtime. He assumed it was about the Tory leader and thought, "The bastards, what are they on about now?" But it turned out that it was Brown's announcement of the funding for Crossrail.

The Prime Minister has gone quite abruptly from the Father of the Nation, to whom we turned to get away from the gimmickry and spin of Blair, to a politician driven by crude electioneering. In 1990-92, we saw just how crude such jockeying for advantage could become. The election was probably decided by the Tory allegation that Kinnock would put up taxes: "Labour's tax bombshell". That was the campaign in which two young men in Conservative Central Office were blooded: David Cameron and Steve Hilton, who is now Cameron's strategic adviser.

The parallels are uncanny between then and now, not just of personnel but of policy. On the Labour side of the battle, Brown was a junior but loyally silent sceptic about the robustness of John Smith's tax plans. Expect a tax slugging match from now until polling day.

Last week's Tory conference theme was the same as Labour's slogan in 1992. "It's time for change." Oh no it isn't, said the voters. We know how the story ended then: the Government put off the election until the last minute and won with a small majority.

Further browsing: electoralcalculus.co.uk calculates election results based on the parties' share of the vote