The academics — the collective term is a theory or, perhaps, an equation of political scientists — seek to forecast the result on the basis of models of what may determine the share of votes for parties. Six articles on this theme appear in the forthcoming issue of the British Journal of Politics and International Relations (published by Blackwell’s).

The interesting point about the six papers is not just the forecasts (of which more later), but what the authors think are the main factors influencing votes. Unlike polls, or pundits’ estimates, or bookies’ odds, the academics have a theory, or rather competing theories and methods. This is not light reading, so I will skip the details as being “somewhat too sensational”, as Miss Prism remarked about the chapter on the fall of the rupee in The Importance of Being Earnest.

The most interesting of the papers is by David Sanders of Essex University, who has been in the forecasting business for more than two decades. He has broadened his approach from emphasising a straightforward link between economic performance and votes, which led him to discount the impact of the Falklands war on the 1983 general election result. Now, he includes the Prime Minister’s ratings, the length of time a party has been in office (the costs of governing) and events, notably, now, the Iraq war. Disregarding other effects, Iraq alone has cost Labour three percentage points in the polls, while the party has, on average, lost 0.06 percentage points each month it has been in power just from being in office.

The interaction of these factors produces a wide range for Labour’s vote share from 35 to 42 per cent. That in itself is neither fresh nor revealing. More interesting is that the model suggests how hard it will be for Labour to rise to the top part of the range. For that to happen, the effect of the war would have to fade completely, Tony Blair’s ratings would need to raise from the current 32 to 35 per cent to 44 per cent and economic expectations would have to increase by a dozen points.

There is also a clear downside risk for Labour if the war effect persists and Mr Blair’s rating and economic expectations do not recover. Hence the potential importance of yesterday’s story about a slight fall in average living standards last year, and why Gordon Brown went on a media counter-offensive last night over the Government’s economic record.

Sanders admits that election forecasting remains more of an art than a science: “empirically informed common sense and no more”. His best estimate is a Labour share of 38 per cent, with the Tories between 29 and 33 per cent, and the Liberal Democrats between 20 and 24 per cent.

Similarly, Paul Whiteley, also of Essex University, uses past shares of Commons seats and poll trends to forecast a Labour vote share of 38 per cent and an overall Commons majority of about 70. This is similar to the estimates of many political journalists: my own guess for some time has been a Labour majority of 50 to 70.

There are big margins of uncertainty, as well as theoretical flaws, in these exercises. Some of the papers either just point to an overall winner (surprise, surprise Labour) or to a majority of between 32 and 100. This leads a sceptic, Professor Cees van der Eijk, of Nottingham University, to describe the forecasts as no more than parlour games, if fascinating ones.

Supporters of the “wisdom of crowds” thesis, as popularised by James Surowiecki in his bestselling book of that name, argue that the projections of large numbers of people are more likely to be correct than those of experts. This has been reflected in political stock markets, such as the Iowa Electronic Market, in which traders invest money in candidates running for office. The weight of money invested provides a forecast of votes for the candidates.

Money also influences bookies’ odds and spread bets. The IG Index yesterday was quoting spreads of numbers of MPs for each party which would give Labour an overall Commons majority of about 60. This would give the Tories about 45 more MPs and the Liberal Democrats a dozen more.

In my own search for a unique insight, I have turned, as always at this time of year, to cricket, and to the irreplaceable work of Frank Duckworth and Tony Lewis in revising targets in rain-affected one-day matches. This is about run-scoring resources, as defined by how many overs are still to go and how many wickets are down when interruptions occur. The precise Duckworth-Lewis formula is as complicated as any of the academic models discussed above. Despite various refinements, this method can occasionally produce bizarre results when a team batting second makes a strong start before rain comes.

The implications are obvious for the Tories: indeed, it may be the only hope for Michael Howard given the weight of polling, pundit and academic forecasts of a Labour victory. If the Tories can get over the partly self-inflicted Howard Flight debacle, and go on the attack, the party can make early gains on Labour. And, then, all it has to do is to pray for rain, and hey presto, a come-from-behind victory.

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