Steve Richards: Brown sails serenely on. But if the Tories behave, they could yet pose a threat to him

In Bournemouth the weather changes hour by hour. Last Sunday night there were gale-force winds. Driving rain fell on Tuesday. In between there has been glorious sunshine, a glowing brilliance that makes you tempted to leap into the autumnal sea.

While the weather oscillates moodily, the Labour conference goes about its business with an awesome and yet strangely eerie predictability. There have been no storms and not even a single gust of wind to make awkward waves. Steadied by soaring opinion polls, the conference ends in a seemingly safe and benevolent climate.

How quickly perceptions change in politics. Six months ago Gordon Brown was being written off in some quarters as a dysfunctional chancellor who would not be able to cope with the demands of being prime minister. It became something of a cliché at the same time to argue that Brown would fail to appeal beyond Labour's heartland. Now Lord Tebbit joins Margaret Thatcher in praising Brown, and Labour's poll lead heads towards the stratosphere.

Brown was underestimated ridiculously. He has benefited since on several levels from the low expectations that accompanied his arrival in Downing Street. Voters are pleasantly surprised. Now it is David Cameron who faces the downside of wildly oscillating perceptions. Not so long ago he was the glittering star of British politics, the engaging leader with a mission to change his party. Suddenly he is seen as flaky, another Tory leader trapped by the temptations to move rightwards while seeking a broad coalition of support.

Oddly the low expectations of Cameron and his party could help them, just as they assisted Brown. Cameron is an inexperienced leader and has at times been weak and contradictory in his strategic approach. But he is an engaging communicator and remains impressively calm at times of crises. These qualities will almost certainly be evident when he – in effect – opens his conference next week with his Sunday morning interview with Andrew Marr. In the context of low expectations, viewers and the media might be reminded of the good-humoured charm that cast a curious spell over his party conference in Blackpool two years ago.

Similarly his party might behave itself next week. The Conservatives are in a febrile state, yet the possibility of an imminent election means a public civil war in Blackpool becomes less likely. Surely even the Conservatives can keep their mutinous instincts at bay if they sense that the following week they will be fighting an election. Here in Bournemouth journalists cannot wait for the drama of Blackpool after the forbidding unity on display over recent days. At the same time, cabinet ministers speculate mischievously about whether the next unofficial leadership contest for the Conservative party will get under way at that even stormier seaside resort. I wonder whether they will be disappointed.

Of course, high drama and public scheming are possible. But it is more likely that Cameron will be saved by the low expectations, and the next instalment in his oscillating narrative will be: "Hold on ... he is not as bad as we thought." After all, it was only three weeks ago that polls suggested the Tories were narrowing the gap over Labour.

That is why the extraordinary political calm in Bournemouth is slightly eerie as well as being formidably impressive. Politics is more volatile than it seems in the comforting bubble of a safely dull conference. Labour under Brown was well ahead until the focus on gun crime in August, which appeared to have a damaging impact on the party's fortunes. Cameron made a tonal u- turn by talking about anarchy in the UK at the end of August, after preaching optimism and letting in the sun shine 12 months ago. But tonal changes of direction, although they reveal a superficiality of strategic thinking, are easier to manage than policy u-turns. Whatever the factors, the polls suggested that Labour's lead was fragile at the end of the summer.

Now Labour soars once more, but could a single vivid violent crime change that position as it appeared to do in August? Will any more economic tremors benefit the governing party as the Northern Rock crisis did? It is quite possible that Labour would maintain its lead, but by no means certain.

In terms of more orthodox political issues, there are also nagging uncertainties. In Bourne-mouth I often hear that Brown has got most of the newspapers on board. That is not quite the case. Media reaction to his speech was mixed. Some of the editorials hinted that there was space for Cameron in the changed environment. If he fills it with more guile and charm than his three predecessors, it is possible that he will get a decent press next week. More widely, the Liberal Democrats are capable of performing poorly in an autumn election with unpredictable consequences. In Scotland, the SNP has the potential to perform fairly well.

In the mean time, policy development is at an earlier stage for Labour than the other parties. Cameron cannot move for policies after his unwieldy but in some cases thoughtful reviews. As ever the Liberal Democrats propose a mountain of detailed policies. Brown was right in his speech to focus on his objectives for public services instead of instigating another inaccessible debate about the means. But in an election campaign he will need to answer questions about how, for example, he plans to make GPs' surgeries open at times when most people could visit them. Yet his NHS review, although progressing well, is not over. There are reviews galore across Whitehall at the moment, which is sensible politics for a new prime minister, but not the basis for an election campaign: Vote Labour and we will announce the outcome of the reviews in a few months' time.

It would be wrong to suggest that those calling Brown to go this autumn are complacently unaware of the volatility. Brownites, like the Blairites of the past, are incapable of complacency. After those 18 years of opposition they still feel they are impostors in power, disturbing the natural order. They urge an early election because they sense it cannot get better than this. But this whole election frenzy comes about partly because Brown's closest supporters know how important it is to the new prime minister that he secures his own personal mandate. It does not take much of a leap to conclude that the sooner he does so the better. This understandable desire feeds the "go early" mood and risks blocking out the more potent question: Why go now when there is no need?

The weather in Bournemouth is more of a metaphor than it seems. In the conference hall it is dry and calm. But outside, politics is less settled. Brown would be taking an unecessary risk to call an election when a storm can so quickly replace the sunshine.

s.richards@independent.co.uk