The Gang of Four would be at home with Tony

It may be that historians will look back and say that it was at some time in the 1990s that politics changed fundamentally. Europe not only turned the Conservative Party into the squabbling congregation of a tin tabernacle: it also raised more basic questions of party doctrine. The Labour Party, which a decade ago would have behaved similarly, as it had done over other questions, notably nuclear weapons, preserved a prudent silence, and looked forward to five years or more of long-awaited power.

Of the two parties, it is Labour which has altered most fundamentally. It is hard to recognise the full extent of the changes Mr Tony Blair has made. The party is now a different creature from what it was in 1994. The most important changes have been organisational and constitutional. They nearly always are, though people do not invariably recognise them at the time because they cannot be bothered with the detail. What has happened is that the old power of the trade unions has been broken.

The person chiefly responsible for this change was not Mr Blair but John Smith. He carried it through, aided by the trade unionist Mr John Prescott, at the Brighton conference of 1993. What happened then and subsequently can be summarised as follows.

The unions' voting strength at the conference has been cut from 90 to 50 per cent of the total vote. Moreover, the block vote has been split, so that delegates can reflect opinion in their unions. This change, admittedly, is largely presentational. It was made so that television should no longer be able to show pictures of various Bills and Berts casually holding up cards representing millions of votes. This hallowed spectacle was, it was felt, bad for the image.

But in the selection of parliamentary candidates, union influence has gone. Candidates are chosen by the system of one member, one vote. This means that the power of the activists assembled in the local party's general committee has gone too.

Likewise with the election of party leader. A third of the electoral college is for MPs and MEPs, a third for the constituencies, a third for trade unionists. Local members vote as individuals. So also do trade unionists, who first have formally to express their support for Labour. The rules laid down in 1994, when Mr Blair was elected, stated clearly that there would be no block votes. Nor were there. Mr John Monks of the TUC and Mr John Edmonds of the municipal workers also made an appeal for unions to refrain from making recommendations to their members about the candidates.

This appeal was largely successful. Indeed, the only union to reject it was, as far as I remember, the transport workers', which supported the claims of Mrs Margaret Beckett. Much good did it do her! By vaingloriously contesting both the leadership and the deputy leadership (which she could have hung on to, without any need for an election at all), she lost both. Serve her right is what I say. I told her, but she wouldn't listen.

Mrs Beckett is a former supporter of Mr Tony Benn. Indeed, she memorably rebuked Mr Neil Kinnock for failing to vote for him against Lord Healey in the deputy leadership contest of 1981. In 1992-94, as Smith's deputy, she was notably unhelpful about the changes he wanted to make. In fact, she tried her best to stop them and to retain the status quo. It would be surprising if she approved of the other changes which Mr Blair has made.

Much to the consternation of his consultants in the Royal College of Spindoctors, it appears that she, Ms Clare Short and Mrs Ann Taylor are more popular with the voters than the leader's favourites, Ms Harriet Harman and Dr Marjorie ("Mo") Mowlam, the femme fatale of the People's Party. In addition to the three former women, the other representatives of Old Labour in the Shadow Cabinet that I would name are Mr Frank Dobson, Mr Michael Meacher, Dr Gavin Strang and Dr Jack Cunningham (what a lot of doctors, though that, as Lady Bracknell would have said, is no guarantee of respectability).

Occupying a pivotal position, neither Old Labour nor truly New, are Mr David Blunkett, Mr Chris Smith and Mr Robin Cook, who would be even more persuasive if only he could manage to conceal his consciousness of his own cleverness. All these and others elected to the Shadow Cabinet are going to be in the real one.

Ms Short has told us that the 1980 amendment to the parliamentary party's Standing Orders is to stay. This requires the new Labour Prime Minister to accommodate all the elected members of the Parliamentary Committee (the formal name for the Shadow Cabinet) in his own first Cabinet, not necessarily in their old jobs or, indeed, for any specified period whatever. Accordingly, Mr Blair could have a reshuffle after a week and still satisfy party rules, though he would be unlikely to till about six months had passed.

Old Labour, predominantly Old Left, have the monopoly of government experience: Mrs Beckett, Dr Cunningham, Mr Meacher and Dr Strang. They are unlikely to be running the Cabinet. If Labour in office is going to be more radical than most people suppose, as Mr Blair has hinted it may be, it will be because of himself and those he finds sympathetic rather than because of the surviving representatives of the Old Left.

But suppose Labour, for some extraordinary reason, does not attain office at all. What then? What indeed! The prospect may be unlikely but is not impossible. The favourite failed to win in 1970, in February 1974 and in 1992. In the last race the tipsters were spectacularly wrong, with only Gallup predicting a Conservative victory, and even then getting the result awry by 7.5 per cent. The average error was 9 per cent, with NOP notching up 11 per cent. Ah well, these things happen, and they may happen again.

The wisdom of the wise is that, if they do, Mr Blair's experiment will be pronounced a failure; he will be out on his ear smartish; the party will be reduced to the state of Brixton on one of its less restful nights, as it was in 1979-81. I cannot for the life of me see why this should happen. It is more likely that the party will move in the opposite direction and form an alliance or merge with the Liberal Democrats.

For what else can it do? Mr Blair's - or, rather, John Smith's - constitutional changes cannot be undone without the greatest difficulty. Humpty Dumpty cannot be put together again. There is now no reason apart from the renationalisation of the railways, which they presumably support while Mr Blair does not, why Lords Jenkins, Owen and Rodgers and Lady Williams should not rejoin Labour. Indeed, Mr Blair sometimes consults Lord Jenkins for the wider view. It has even been suggested that he might find himself restored to a Labour Cabinet as Lord Privy Seal or something of that sort. It may not happen. I do not think it will. Still, it indicates an element of reconciliation between Labour and the former Social Democrats brought about by the changes Mr Blair has made.