THANKS to the distortions of Britain’s political geography, Labour retains a clear advantage ahead of Tony Blair’s confirmation, expected tomorrow, that the election will be held on May 5. Even though two polls in the past fortnight have shown Labour and the Conservatives on level-pegging, the prospects of the Queen asking Michael Howard to form a government on May 6 are remote.

The latest Sunday Times/YouGov prediction indicates Blair’s majority will tumble to 70, with Labour winning 36% of the vote and 358 seats, the Tories 34% (195 seats) and the Liberal Democrats 22% (62 seats).

The future is always liable to spring surprises, however. One party might campaign much more effectively than another so it is possible the Conservatives will edge ahead in the popular vote. However, they need a six-point margin to become the largest party and a 10-point lead to win outright. Nothing in recent polls suggests the Tories will scale this mountain.

Nevertheless, they could inflict a blow on Blair’s leadership. Our forecast of a 70-seat majority is about the minimum that would allow him to claim a real victory. Even that figure would cause 45 Labour MPs to lose their seats and leave Blair open to backbench Labour rebellions that could derail his plans for public service reform.

If the Conservatives and Liberal Democrats make further inroads into Labour’s majority, Blair risks being seen by many in his own ranks as an electoral liability. Should the majority stay above 80, the prime minister would feel justified in celebrating not just three victories in a row, but three big victories.

What will determine the size of Labour’s majority? Probably the biggest factor will be the battle of the campaign agenda. Recent YouGov surveys suggest a clear pattern. When the political news is dominated by “Labour” issues, such as the economy and the public services, the party enjoys a 4-6% lead, which would give Blair the kind of majority he craves.

But the gap narrows sharply when “Conservative” issues come to the fore, such as crime and immigration. So watch for ferocious attempts by both parties to dominate the agenda.

It is in this context that the recent diversion over Howard Flight, the Conservatives’ former deputy chairman, has been such a headache for the party. It is not that the public are likely to care greatly about Flight’s fate. Rather, the episode robbed the Tories of six days of opportunities to stress their strengths.

Plainly, strategists from all parties will scour polls over the next few days to see whether the public mood has changed since Easter. As a pollster, I should like to be able to say that pollsters, and YouGov in particular, will be spot on with every figure. Honesty compels me to warn against anyone believing in the precision of our data.

There are two reasons for this. The first is we are all subject to laws of probability. On samples of 1,000-2,000, even the most carefully conducted poll is liable to errors of 2-3%.

The second reason is that polling is as much an art as a science. All pollsters apply judgments and these vary from pollster to pollster, and from election to election.

In 1992, the polling industry fell flat on its face. Every company showed John Major heading for opposition. Around midnight on election night, it became clear they were all wrong.

Since 1992, the industry has changed massively. Two famous names have disappeared from political polling for the media: Harris and Gallup. Three new companies have arrived: YouGov, Populus and CommunicateResearch. None of these operates in the same way the industry did in 1992.

Conservatives claim the polls have consistently overstated Labour support, not just in 1992 but in 1997 and 2001. This is largely true but since then, there have been further changes to pollsters’ methods, mainly to exclude electors who are unlikely to vote. This tends to reduce Labour’s lead, typically by about five points.

So the Tories cannot count on the polls overstating Labour for the fourth time. But the pollsters will be awaiting the results as anxiously as any politician, to see if we have finally exorcised the ghosts of 1992.

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