It was a great personal triumph for Michael Foot. As results came in from the European elections on Sunday night, with Labour scoring little more than 15 per cent, it was, at last, time to reassess the achievements of Labour's most underrated leader.

In 1983, led by the great helmsman, Labour scored a stonking 28 per cent of the vote and saw off the pesky SDP. Annoyingly, Margaret Thatcher won a landslide victory and this has diverted historians and the media who have a tendency to chase off after trivia. As Tony Benn remarked at the time, the real import of the result was not the Tory win but the registering of eight-and-a-half million votes for socialism.

It is now common to note how many fewer votes than that Labour scored in the European elections. Indeed, on one of the most gripping political nights of the year (blink and you missed a small swing towards the Centre Right in Latvia), Labour's vote was so low that, never mind Michael Foot, it would have provoked Ramsay MacDonald and Keir Hardie to call an urgent strategy meeting. Sunday's result showed Labour registering only a tad more than half of Foot's vote.

Yet to compare the modern Labour Party unfavourably with Michael Foot's, a grasp of mathematics is only one requirement. The other thing you need to have is a defective memory.

It is not necessary to hold Gordon Brown's leadership in high regard to assert that between 1979 and 1983, Labour was immeasurably worse. It was ideologically split between people whose ideas were plainly mad and others who were merely completely wrong about almost everything.

The split produced a contest for the deputy leadership that dragged in all its main players. The most electorally attractive figures left the party altogether.

The party's candidate for prime minister would have been a more credible candidate if he had been put forward for a minor literary prize. And its election manifesto was so obviously rambling, impractical and unpopular that a member of the Shadow Cabinet dubbed it “the longest suicide note in history”. The correct response, therefore, to hearing that Labour is now doing worse than in 1983 is not just to say “gosh”. It is to ask “why?” And the answer is to be found in changes to the electorate that have fundamentally altered the nature of politics.

In his book Tides of Consent, the American political scientist James Stimson argues that voters can be divided into three groups. The first group he calls “the Passionate”. These are people “who care a great deal about public affairs, have strong views, and form lasting commitments to one side or another”. In what is no more than a common-sense observation, Professor Stimson argues that these people don't settle elections. They can't because they don't move their vote and tend to interpret political events in a way conditioned by their existing view.

A second group he labels “the Uninvolved”. These are “people who think politics isn't important in their lives (and they are probably right), don't pay attention and don't want to be bothered”. The Uninvolved often don't vote, and what moves them politically hither and hither has a random character, with one movement cancelling out another.

Which leaves Stimson's third group - “the Scorekeepers”. The Scorekeepers “are non-ideological pragmatists who trust or distrust each side equally. They tend to see politics not as a contest of world views, but merely as alternate teams of possible managers of government, each contending that they can do a better job. The Scorekeepers are not choosing directions in their votes, they are hiring managers.”

It is this group - pragmatic, ready to change sides, involved enough to care - that really accounts for Professor Stimson's political tides.

What we have seen in the past 30 years is a shift from “the Passionate” group, swelling the ranks of “the Scorekeepers”. This changes politics in two ways. First, it makes elections more volatile. Votes are lent to parties, rather than given them for life. A party that wins a healthy majority in one election can lose by a landslide in the next. The base vote that was once prepared to turn out even for Michael Foot is much diminished.

The second change is that politics has become more pragmatic, less partisan, more inclined to a sort of cool centrist position. Politicians who seem obsessive or extreme are unattractive to the Scorekeepers. The ability of leaders to communicate matters more as voters “interview” their next prime minister before hiring him or her. The quality of the chief executive is more important than the party's identity. Try to fight an election with a leader even slightly inferior to the alternative on offer and you risk being slaughtered.

These two changes make Labour's poor position more readily understandable, but still don't explain why the change has taken place. Why has there been this shift from the Passionate to the Scorekeepers?

Professor Stimson believes that committed voters are ideologues. I don't think it is so simple. I believe that people's political positions aren't generally the result of book-learning and abstract thinking. They are a statement of identity. People choose their politics as a statement about themselves. And often they sign up to support a party as a way of joining a tribe.

In British politics, people have long chosen their tribe along class lines. Labour could rely on working-class solidarity. Voting Conservative was part of the middle-class package. There was a big gulf between the two, and moving from one to the other seemed unthinkable for many people. It would have involved changing who they are.

Tony Blair was the Scorekeepers' pick for PM. He didn't just shift the ideology of the Labour Party, he also changed its identity. He made it possible for lawyers living in big houses to vote Labour. He also made it possible for factory workers living in Yorkshire not to vote Labour.

So Labour's poor election result last week means much more than that Gordon Brown is a broken leader and, ahem guys, it might be a good idea to get yourself another one. It means that the old politics of safe seats and massive core votes is being altered for ever.

Labour can lose in Wales, the Tories can be defeated in Guildford, UKIP can rise today and it can disappear tomorrow. The era of the Scorekeepers has arrived.

daniel.finkelstein@thetimes.co.uk

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