ABOUT a year ago, beneath the surface of the polls, the tide of British politics changed direction.

It is easy to concentrate on headline findings and today’s are undeniably dramatic. The Tories are ahead after 134 consecutive months of Labour leads, a series broken only during the surreal period of the fuel protests.

At 36 per cent, however, the Conservative rating is not enough to bring them victory. So the most important message may be one hidden deep down in the poll’s workings.

Polling political attitudes these days involves making a number of adjustments and weightings to try to ensure accuracy — taking account of the people who are very hard to poll at all, and those who, if polled, prefer not to disclose their views.

Since the 1992 election, when all the polls were so badly wrong that they failed even to predict the winner, pollsters have used how people say they voted at the previous election as a way to weight their samples and try to ensure political balance.

For nearly 20 years it has been a defining characteristic of British politics that people did not want to admit either that they had, or that they would, vote Conservative.

This, as much as anything else, has been a measure of how unpalatable the Tories have been: normal decent people have been too embarrassed to concede that they might vote Conservative. They were dubbed the “Shy Tories” — Tories who told pollsters they didn’t know how they would vote, or that they might not vote at all, or even that they planned to vote for another party. As a result, the raw data which pollsters assemble from their interviews produce a substantially different picture of the political balance than the same figures once they are adjusted.

Early last year, after a short period of neutrality, the spiral of silence reversed itself. Polls began to find that the proportion of former Labour voters saying that they didn’t know how they would vote next time began to climb, while the proportion of Labour supporters saying that they were sure to vote began to fall. Pollsters have been adjusting Labour’s poll support upwards to take account of this growing number because all empirical data tell us there is about a 60 per cent probability that, however reluctantly, if they vote at all they will end up voting Labour again. Without this adjustment the Conservative lead in today's poll would have been 2 per cent higher.

SO in place of Shy Tories we now have Bashful Blairites, people unwilling to admit to pollsters or their friends that they still support the Prime Minister. Once so fashionable, new Labour has now gone out of fashion. This is very difficult to reverse. One day they may look on this as the beginning of the end. Just ask John Major.

The new spiral of silence, however, also brings with it a risk for Conservatives. They might believe insufficiently adjusted polls and think themselves to be much closer to power than they really are, halting any impulse to respond further to the new centre of gravity of public opinion, misjudging their message and tone as a result.

This risk is all the greater for the fact that the spiral of silence among Labour voters is highly unlikely to unwind on June 10. On that day there is a glut of mid-term elections, but most voters see them as neither important nor interesting enough to engage with. So Bashful Blairites are particularly likely not to vote in the European elections, the local elections or London mayoral election.

The result? The Tories are likely to do deceptively well in June. It is when it matters — at the next general election — that history suggests that the spiral of silence will unwind.

So politicians would do well to remember how to read a poll properly. The seductive stuff is in the headlines. But with voters busier than ever before, bombarded with communications, bruised by successive governments that seem to have let them down, they don’t spend very long studying the content of what politicians say. They base their voting decision on the view they hold deep down of the general reputation, motives and values of a party.

So it is far beneath the surface where the lasting truths of opinion polls are usually to be found.

The author is director of Populus, pollsters for The Times

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