Throughout the spring, the polls' raw figures showed a quite consistent picture. Conservative support was averaging 23 per cent, Labour 57 per cent and the Liberal Democrats 15 per cent. For each party, individual polls showed support of 3 per cent more or 3 per cent less than these levels, but Labour maintained a more or less steady lead of about 34 per cent.
Then the political climate changed. After Mr Major called the leadership contest on 22 June, Tory support jumped: the Tories moved to an average of 29 per cent, Labour to 55 per cent and the Liberal Democrats to 12 per cent. Again there were small variations in individual polls, but the Tory share rose by an average of 7 percentage points,Labour and the Liberal Democrats were down by 3 each, other parties by 1. The Labour lead was down to 26 per cent.
But MORI's poll - based on face-to-face interviews with 1,938 adults between 21 and 24 July - showed the Labour lead back to 33 per cent, with the Tories down to 26 per cent, Labour up to 59 per cent and the Liberal Democrats still on 12 per cent.
The grim news for the Tories was emphasised by a drop in those satisfied with the Prime Minister's performance. There was also a steep fall in the "feel-good" factor: the difference between those who expect the economy to get better over the next year and those who expect it to get worse.
Equally worrying for the Tories are the voters' views on which party is best equipped to deal with important issues. The most important of all is health care: 61 per cent say it will be a key issue in determining how they will vote at a general election. By a margin of eight to one, against five to one a few months ago, those people say Labour would be better. Unemployment is decisive for 53 per cent of the electorate: they say Labour would be better by more than seven to one. Education is important for 52 per cent: they prefer Labour's approach by a margin of four to one.
And so it goes on. On the top 11 issues - including law and order, the economy, taxation, pensions, housing, and public transport - Labour has a lead among the people who say that the subject will influence how they vote. Only on defence and Northern Ireland - 12th and 13th in the electorate's order of priorities - do the Tories lead.
l The author is chairman of MORI and Visiting Professor of Government at the London School of Economics.Reuse content