John Rentoul: The Tories' lion has failed to roar

There won't be an election before May, but Cameron has failed to capitalise on economic woes and looks less of a threat than ever

Well, we know now. When Gordon Brown became Prime Minister three months ago, the great mystery that shrouded the future was how the voters would respond to a choice between him and David Cameron. It was difficult to predict what Brown would be like when he was in charge. Or how Cameron would be seen once we knew what he was up against. So the crystal ball-gazers (including me) said it was all a bit cloudy and that we would have to see how the opinion polls settled down after the party conferences.

As it turned out, we did not need to wait that long. The jury foreman has shuffled into the court of public opinion and delivered the verdict. It is good for Brown and bad for Cameron.

In each case, it has been a rival in their own party who has been the most convincing witness. John Reid, who was home secretary three months ago, testifies to Brown's strength. His announcement last weekend that he would be standing down as an MP was an admission that the new Prime Minister had made a good enough start to make it pointless for him to hang around. Reid is a clever judge of politics and knows that if and when Brown eventually stumbles, it will be to the next generation – David Miliband and Ed Balls – that the party will turn.

On the Conservative side, it is Michael Portillo who testifies to Cameron's weakness. As the man who was beaten to the Tory leadership by one vote in 2001 helpfully pointed out on television last week, Cameron and George Osborne, his shadow chancellor, appear lightweight and inexperienced against Brown and Alistair Darling.

On the face of it, this is extraordinary. When queues started to form outside Northern Rock branches, it was a moment when it seemed that everything could change. It sent minds racing back to 1992, that formative year for so much of politics on both sides of the Atlantic. That was the year the ERM crisis destroyed Tory credibility on the economy. Cameron and Osborne know that they need something similar to happen to Brown's reputation for competence.

It was also the year of the Clinton campaign, studied as closely by Cameron and his friends as by the New Labour inner circle. It was from that campaign that a generation of political obsessives learnt that "speed kills" – James Carville's graphic slogan about the importance of tempo, the news cycle and instant rebuttal. Indeed, the Cameron operation moved up a gear in August, becoming quicker and more aggressive. This was despite its being split geographically between the leader's offices in a Palace of Westminster annexe known as Norman Shaw South and an election-style war room next to Millbank Tower half a mile up the Thames.

Hence the speed with which Cameron reacted to the run on Northern Rock when it spilled on to the high streets nine days ago. Within 24 hours he had written an attack on the Government for The Sunday Telegraph in vivid prose: "Though the current crisis may have had its trigger in the US, over the past decade the gun has been loaded at home. Under Labour our economic growth has been built on a mountain of debt."

Then, on Monday, he could have gone for blood in a speech in the City of London. In contrast to the striking metaphor of the loaded gun, however, the speech was homogenised pap of the kind that pours out of any Westminster computer. What happened?

My guess is that team Cameron got the results of the focus groups in and realised that blaming it on Gordon was counter-productive. As Populus found out in a poll carried out while the crisis was at its height, most people did not think Northern Rock's problems were the Government's fault. The crisis did damage trust in Brown and Darling's ability to deal with economic problems – their rating dropped five points in the month. But Cameron and Osborne's dropped by nine points, thus extending Labour's commanding lead as the best party on the economy. Hence the apparent paradox: Darling did an indifferent job of reassuring people, although he got it done in the end, and Labour ended the week with a solid lead in the opinion polls. As Alan Watkins writes on page 38, this was enough to reignite speculation about an October election, even though nothing has really changed.

Once again, the Tories and many in the media have been wrong-footed. There is not the remotest chance that Brown would take the risk of matching George Canning's record as the shortest-serving prime minister. If Brown lost an election on 25 October, he would have served for 119 days, as did Canning, a Tory who died of pneumonia in 1827. The risk of losing may seem small, but it is not one that any prime minister would take.

Allowing others to speculate is another matter. It works wonders for party discipline. Brown is likely to win the vote in Bournemouth today to abolish contemporary motions, because delegates think there may be an election soon. And it confuses and dismays the Opposition.

No, the election will not be until May next year at the earliest. Like most prime ministers, Brown likes the job and thinks he is good at it. The opinion polls of the past three months do not contradict him. The fears of the Blairites and the hopes of the Conservatives have not been realised. The electorate – about 40 per cent of it, anyway – likes his solid style. "Not flash, just Gordon," the slogan with which Saatchi & Saatchi clinched the Labour advertising account, was a masterpiece of zeitgeistery.

Just as importantly, the shine has come off Cameron. His "broken society" theme was applauded by The Sun, the Daily Mail and The Daily Telegraph – Camero-sceptics all – but the polls did not move. The greenery of his Quality of Life review group made no impression at all. And the attempt to blame Brown for people borrowing more when interest rates were low was quickly aborted.

Cameron has repositioned the Conservative Party as much as he can, and he is a personable leader. But his achievement was flattered by the unpopularity of Tony Blair. By comparison with him, he looked promising. By comparison with Brown, the lack of substance becomes an issue.

The fact that the election is really at least seven months away cuts both ways, however. Brown believes – this is an observation from the history of prime ministers, rather than a claim to know exactly what is going on in the Prime Minister's brain – that the longer he is in office, the greater the bond of trust he will develop with the voters.

This is contradicted by all the evidence that political trust is a wasting asset. Other unexpected events may erupt that do not turn out to be as benign in their impact on the Government as the Northern Rock crisis. And the breathing space gives Cameron and Osborne the chance to shed the callow public relations men image. But the balance of doubt has moved. It was: can Gordon do it? Now we know he can, and it has become: can Dave recover?