Bruce Anderson: In a body-language election there can be only one winner

The Tories had always intended to start their election campaign before Twelfth Night and to maintain a relentless pace until polling day. On one point, we can be certain. The planning will be thorough. Mr Cameron and his team do not believe in improvisation. But whatever the degree of planning, there is another certainty.

Most of the tens of millions of words which all the parties are about to emit will be wasted. The average voter will not absorb more than a tiny percentage of them. But some will stick. The voters will form an overall impression. This may not be especially articulate. But it will be decisive.

There is a further vital point on which no certainty is possible. Will the actual election campaign matter? If it does, it will be in a minority. Over the past 30 years, only once has a campaign had an important effect on the outcome: in 1992. Otherwise, there is no reason to believe that the final frantic weeks altered anything.

In 1979, the Tories had everything planned. They then made a hideous strategic error. They started a week later than Labour did. This meant that the Tories spent much of the next four weeks on the defensive, rebutting Labour smears which had enjoyed an uncontested week to embed themselves. It was nerve-racking for the Tories at HQ – and it did not matter. Enough voters had made up their minds that it was time for a change.

But there are three reasons for thinking that this campaign might matter. Over the past few years, the sovereign people has become much more volatile. Tribalism is not what it was. Many more voters have many fewer preconceptions; look at the way in which turnout has fallen. The second, related reason is that the days of the uniform swing are over.

Fifty years ago, the swing in Billericay, Bradford and Bournemouth might be within one percentage point. Today, we can expect regional variations, local variations, personal variations. The expenses degringolade will also affect a number of contests. It will still be a national campaign, which will not disintegrate into 646 by-elections. Even so, MPs or candidates – for good or ill – will be able to make a far greater contribution than their predecessors could a generation ago.

The third factor is the debates, assuming that they do take place and that the minor parties are unable to use the Representation of the People Act to derail them. It is surprising that it has taken the UK so long to get round to electoral debates. For years, the underdog would issue a challenge, the overdog would find a thinly disguised way of saying, "why should I take the risk?" and the public would shrug its shoulders. This time, David Cameron felt that if he merely said, "Nice try, Gordon, but what would you do if you had a 10-point lead?" he would come across as frit.

Frit or not, some senior Tories would have chanced it. Apart from the gratuitous introduction of uncertainty, they were worried about the Liberals. For years, both the largest parties have claimed that a Liberal vote was a wasted vote. But once the wasted vote is granted TV time, might it not acquire legitimacy? That argument could have been conclusive, under a different Liberal leader. Menzies Campbell was never more than Roy Jenkins after a lobotomy. But he possesses a certain grey-haired plausibility. He knows how to make platitudes sound sonorous. Vince Cable is much the most over-rated figure in modern British politics. He is a poujadist masquerading as a central banker. Yet one should never underestimate poujadism's enduring appeal.

Poujadism rests uneasily with Nick Clegg, as does appeal. Mr Clegg has a problem. He is more intelligent than either Mr Cable or Mr Campbell and he has a bedrock of conviction. But it is a conviction that dare not speak its name. Mr Clegg, who is only about a quarter British, believes in a federal Europe. That is the cause which brought him into politics; that is a subject which could make him eloquent. It could also cost his party a lot of seats. Mr Clegg feels unable to be frank. So he is condemned to be insipid. Serves him right.

Anyway, and whatever the Tory augurs conclude from their scrutiny of the Liberal party's interstices, there is no going back. The late Gordon Reece was that uncommon phenomenon: a PR man who understood the public. He had a dictum, which has never been more relevant. "When they're watching politicians on telly, real people do not follow the argument in detail. They drift in and out of concentration; they might even drift in and out of the sitting room. But they ask themselves one question: 'Is this a nice person or a nasty person who has come into my living room?' If the answer is 'nasty', you have lost."

Assuming that Mr Cameron does not suffer a debating implosion – highly unlikely – he ought to be favoured by a body-language election. Ken Clarke defined the task yesterday: to come across as "a potentially good prime minister who will lead a better, more reputable, more responsive type of government".

That is hardly an impossible challenge – and there is another important dictum, which should also work in Mr Cameron's favour. The late Dick Scammon, the sometime doyen of American political scientists, used to say that in every election, despite the best efforts of the handlers, there would be moments of political nakedness, when the voters would see the candidates as they really were. This would have a dramatic impact on the outcome.

It is quite likely that between now and election day, David Cameron will project himself as a decent man who wants to be prime minister in order to do his best for the country, while Gordon Brown will come across as a driven, feral creature who is desperate to remain PM because his ego would crumble under the humiliation of defeat. If that did happen, the Tories would win.

But a reassuring body language is not enough. A general election is not the same as the final exams at charm school. In conditions of economic crisis, dislikeable but tough could still make inroad on well-meaning but not strong enough: inroads sufficient to deny an overall majority.

Gordon Brown will try to fight the third re-running of the 1997 election, accusing the Tories of planning to slash the NHS, destroy state education and condemn OAPs to starvation. David Cameron has spent four years trying to ensure that those lies will never reach cruising altitude: four successful years. He has won that body-language battle. The voters will simply not believe that a government led by Mr Cameron would destroy the health service.

The Tories intend to reinforce this impression by manifesto commitments to reforms in health and education, which will use the language of choice in an appealing way. Hitherto, when the Tories spoke of choice, it sounded as if they were hoping to subsidise their supporters to go private at cheap rates. Now, the aim is to persuade everyone that choice is for them.

So the Tories can concentrate on persuading voters that they can be trusted to sort out the economy. Before he became party leader, David Cameron used to enjoy cooking, and still does, on the rare occasions when there is time. He never ventured on haute cuisine; his forte was roasts and proper breakfasts. But he was also good at bread; knobbly, healthy brown bread which would pass every glycaemic index test. He now needs more roughage in his rhetoric.