John Rentoul: It was the first time I had seen the Prime Minister blush. And he has good cause to

Blair is like a cartoon character that has run off a cliff

It was the first time that I have seen Tony Blair blush. At his news conference last week an American journalist asked an unusual question. Should European governments respond to the ageing of their populations by encouraging larger families or should such matters be left up to individuals? The Prime Minister muttered awkwardly: "Well, I have done my bit - four - that is very good," before stumbling on. "I don't think you can do this artificially." At this point, the po-faced Downing Street transcript ought to have recorded, in square brackets: "Laughter - collapse of statesmanlike posture".

Blair hardly ever mis-speaks. One of his strengths is the instinctive carefulness of his diction, his extrasensory perception of traps and hostages in words and phrases before he uses them. Indeed, the rest of his news conference was the normal monthly masterclass in what might be called precision optimism. It is a tribute to his way with words that Blair is still where he is. Since the election 10 months ago he has had no visible means of support, like a cartoon character that has run off a cliff. Yet he is a weightless politician. There is nothing to hold him up, yet there is nothing that can pull him down, provided he remains manoeuvrable enough to avoid the gravity switch of a vote of no confidence among Labour MPs.

Which explains last week's finely calibrated language on the Education Reform Bill, to be published on Tuesday and on which there will be a momentous vote in the House of Commons in three weeks' time. He was "absolutely sure" he would get the support of the "vast majority" of Labour MPs, but went on to admit with apparent candour: "The question is whether we manage to get enough to get it through with Labour votes alone." That is the question on which the conventional Westminster wisdom is that it would be "unsustainable" if he had to rely on the Conservatives to get the Bill through. But when Patrick Wintour, the new political editor of The Guardian, put that question to him, he said: "You mean, I should get the legislation through and say, 'Now I think I should quit'? No, I don't think that is very sensible."

It was only a statement of the obvious. The vote on the Iraq invasion would have been lost had the Tories voted against it - the Labour rebellion of 139 was easily enough to wipe out Blair's majority, which was larger in 2003. That is hardly a happy precedent, but no one said that Blair's position was unsustainable as a result. Equally, though, it would be unwise for Blair to say he does not care how many Labour MPs vote against the Education Bill because Tory support will ensure it goes through.

Therefore, he will fight with energy, cunning and passion, as he has done periodically, to persuade his party to follow him. Yet it is a measure of failure that he has to resort to such tactics to stay airborne. After all these years he still relies on his own verbal wizardry and personal persuasiveness to keep the Government's ideology afloat. Instead of creating and sustaining a cadre of followers, or even a coalition of interests behind the New Labour reforms, Blair has watched support flake away until only the tiniest band of true believers is left. In that respect, he is quite the opposite of Margaret Thatcher.

Hence the compromises and verbal gymnastics required to get the Education Bill through. For the next three weeks at least, the Bill will be presented as if its only concern is to promote the interests of the poor, when its real objective is to raise standards across the state sector.

Hence, too, Blair's cleverest verbal construction of New Labour as ideologically dominant. If only. His response to a question last week about Labour's defeat in the Dunfermline by-election was one of glottal-stopping machismo. "There is only one group of people with a serious policy agenda and that's us. I mean the Lib Dem leadership debate - who's got a serious policy agenda? That's wha' I want to know. I can't see i' anywhere." The Conservative policy commissions he dismissed as "unconvincing". Meanwhile, he said, behind the daily drizzle of bad news stories, the NHS, for example, is being "reshaped and changed in a fundamental way". In two or three years' time, waiting lists will have been more or less abolished.

Maybe they will. But the argument for the mechanisms that are beginning to produce results - choice and competition - is as far from being won as ever. That was the hidden lesson of the most important speech made last week. It was called "The Blair Legacy? Choice and Competition in Public Services", and was delivered by Professor Julian Le Grand, who was the Prime Minister's health policy adviser until last summer. It was a powerful demolition of the reflex objections to more choice that still grip most of the Labour Party.

Le Grand argued that choice and competition will make public services "not only more responsive and efficient but also - contrary to popular belief - more equitable and socially just". It is a myth, for example, that it is the middle classes that (a) want choice and (b) benefit most from it. He cited surveys showing that women, the poor and the less well-educated are most in favour of choice in public services. And he pointed out that it is the middle classes that are better at manipulating the restricted-choice systems in health and education. GPs tend to spend more time on consultations with the better-off. And it is only the well-off who can buy houses in the catchment areas of popular schools. Where pilot schemes of choice systems have been tried, they are taken up just as enthusiastically by the less well-educated, the poor and the non-white. In the health service, "patient choice advisers" are so popular that the idea has been copied in the Education Reform Bill.

Yet almost none of this debate about what works in real trials has been taken up in the Labour Party, which, as a membership organisation, is almost dead. The only politician in the audience for Le Grand's lecture was David Willetts, the Tory education spokesman - a stealthy incursion on to Blair's centre ground.

The few Labour members who remain in the party seem transfixed by an idea of "privatisation" of public services that seems unchanged since 1983. The Labour debate about education seems rooted in an even earlier era, as if a fully comprehensive system were being designed from scratch and none of the social polarisation of schools over the past four decades has happened yet.

Blair sees the danger of this, of course, but it is an embarrassment that Blairism has made so little headway with his own party and the wider leftish political classes more generally. Perhaps he is right to blush.