Recent general elections have thrown up shorthand terms to characterise the key voters of the minute, whose decisions are expected to decide the result and on whom campaigning efforts will be most concentrated. In the 1980s, Margaret Thatcher won elections by successfully appealing to Essex Man. More recently Worcester Woman and Mondeo Man have been the shorthand terms of choice.

It is not accidental that two of these three familiar tags are geographical. The theory of the key voter is that only a small proportion of voters will be prepared to switch parties, and that only in a small proportion of seats – the marginals – will it make any difference if they do. These convenient stereotypes are all about maximising campaigning efficiency by targeting the right voters in the right places.

But if the parties are looking for a successor to Mondeo Man in 2005, thinking along the same lines as in the past, they may be making a big mistake. Disillusionment and ‘disengagement’ are the order of the day. There seem few signs that many voters are wavering between Labour and the Tories, ready to be captured by the more convincing campaign; but what they do seem to be doing, in droves, is deciding that they might not vote at all or that they will make a protest vote for a party that cannot win.

This is not confined to a handful of swing voters in the middle of the political spectrum, but is eating into the ‘core’ vote of both major parties – voters who would not even consider voting for the other major party, but can no longer be relied upon to make their vote count at all; and, for the moment at any rate, the signs are that Labour will suffer more than the Conservatives.

In Mori’s January 2005 Political Monitor survey, we found that 72 per cent of Conservatives, 64 per cent of Liberal Democrats but only 55 per cent of Labour supporters say they would be certain to vote at an immediate election. This is a much bigger differential than we have found at any previous election. Might this mean that it is not too late to close it?

It may well be, therefore, that there is far more to be gained and lost by concentrating on turning out disillusioned ‘core voters’ than on trying to win over voters from the other party. And this in turn implies an essential difference between the familiar position and the one that faces the parties in 2005. Traditionally, both parties have been targeting the same ‘swing’ voters. But if turnout rather than swing is going to decide the election, each party will be concentrating separately on their own strongest areas rather than competing with each other where they are both weak – and that in itself may make campaigning less hit-and-miss, more efficient and more effective.

Another thought. Of course, it is the marginal constituencies that matter most; but who is to say what is a marginal? If turnout falls too far among core voters, freak results are possible – a little real swing will go a long way, and even apparently ‘safe’ seats might not be as safe as they look. After all, who could have believed that Labour could lose an election in Islwyn, Neil Kinnock’s former seat? Yet it fell to Plaid Cymru on a 47 per cent turnout in the 1999 Welsh assembly election.

So perhaps Labour’s new target voter should be ‘Islwyn Man’? Not voters in South Wales, of course, but the millions across the country who voted for Neil Kinnock in 1992 and are now not sure whether or not to vote for Tony Blair in 2005.