Andrew Grice: The fight is not yet won – and Cameron knows it

When David Cameron addressed staff at Tory headquarters about his party's conference starting tomorrow, he said Labour was "absolutely right". About one thing, anyway: that he had "not yet sealed the deal" with the electorate. He added: "The real danger we have at the moment is in any way looking complacent."

The word has gone out from the Tory high command that there should be no television pictures of champagne-swilling frontbenchers, MPs or staff celebrating the astonishing progress the party has made.

At a time when the public feels the chill of an imminent recession, the last thing the Tories want is to look as if they are taking the voters' support for granted. "We will be tough on complacency and the causes of complacency," one senior Tory said.

In his speech on Wednesday, Mr Cameron will carry on where he left off a year ago, when he did a remarkable walkabout on stage and spoke without notes. This time, his mission is to look like a serious prime minister-in-waiting, so he will speak from a lectern. For all of the Tory criticisms of Gordon Brown, they know the economic storms have thrown the Prime Minister a lifeline. They are not wrong in thinking that, without it, he might have been thrown overboard. Mr Brown is back in the game; Mr Cameron must now raise his. Mr Brown had a much better conference than he might have done, even though his impressive speech has been overshadowed by the messy announcement that Ruth Kelly will stand down in the reshuffle next week.

Watching Mr Brown's speech, Mr Cameron's said his call for a "new settlement for new times" lacked detail and was pitched to his party, not the country, giving the Tories the chance to do the opposite. Privately, some senior Labour figures agree.

Until a few weeks ago, the Tory leadership thought all the pressure during the conference season would be on Labour. Yet the threat of financial meltdown has changed the game, posing real challenges for the Opposition.

Mr Cameron must answer Mr Brown's charge that he is a "novice," a line which bolsters what Labour insiders call his "hold onto nurse for fear of something worse". Portraying Mr Brown as the architect of Britain's problems and contrasting Labour's obvious divisions with Tory unity might not be enough. The Tory claim that Mr Brown "failed to fix the roof while the sun was shining" has hit home. But the Opposition also needs to answer the "What would you do?" question. It failed to on issues such as Northern Rock and the abolition of the 10p tax rate. So we can expect some detailed measures to help Britain through the economic downturn as part of Mr Cameron's "Plan for Change", his slogan borrowed from Barack Obama.

Although the Cameroons insist the economic and social agendas are too halves of the same coin, shadow ministers admit privately the Tories need to show the public they are focusing on bread-and-butter economic issues.

Another dividing line has been blurred by recent events. Mr Cameron's call for a "post-bureaucratic age" and smaller state struck a chord with voters who felt Labour's top-down solutions had not transformed public services. But at a time of economic uncertainty, the public may look to a government for protection. If Mr Brown handles the crisis well, the Tories' 20-point lead in the polls may yet be shown to be more of an anti-Labour protest rather than a positive endorsement. The tide of events which seemed to be flowing the Tories' way until very recently has now become a dangerous whirlpool; no one knows what will happen when the turbulence stops. As Mr Cameron told his party workers: "That deal is never sealed until that cross goes on the ballot paper."