He could be the longest lived PM of all. The trouble is, stuff happens

This will be looked back on as the year in which Tony Blair might have fallen but did not, and at the end of which he was in a far stronger position than he was at the beginning. This was the year in which he might have ensured that he survives in office longer than any other 20th-century prime minister. He overtakes Harold Wilson in February and, assuming he wins the election, he overtakes Asquith and Churchill next December. If he stays in Downing Street for as long as he told us this year that he would like, serving for the whole of a third term but not standing for a fourth, he would in November 2008 outdo Margaret Thatcher's record of 11 years and 209 days.

The odds must surely be against it, if only because stuff happens. The conventional wisdom is that Blair might last two years after the election. But if he can do two, why not four? It is true that, apart from ministers afraid of Gordon Brown taking over, Blair does not have a constituency that has a vested interest in his survival. Yet he has survived. Liberal middle-class opinion is overwhelmingly hostile, and journalists are the most extreme subset of that class. My colleague Alan Watkins wrote last month that "of all the people I know - friends, relations, acquaintances whether close or slight - not one of them intends to vote Labour at the election". Yet the opinion polls currently suggest that about 37 per cent of the general population intends to vote Labour.

That fact together with its obverse, the continued electoral weakness of the Conservative Party, is the main reason why Blair survived the past 12 months. We still do not know quite how close he came to standing down. There is still the mysterious story that he suggested, in April, that he should pre-announce his departure from office towards the end of the year. That was odd enough. Even odder was the point of the story, which was that Brown sought to dissuade him from making such a statement. Blair's reaction, when the story was reported in The Times in September, was: "Oh yeah?" His aides, however, do not deny it, and one of Brown's allies admits that the Chancellor made a terrible mistake in not publicly cashing Blair's cheque, post-dated as it was.

Brown was reported to have said it was a bad idea because it would mean six months of destablised government. I am not sure he could have encouraged Blair to pre-announce in any case, because other senior ministers were allegedly present. The whole thing may have been a stratagem by Blair to rally his supporters - it was after this that his cabinet colleagues queued up to beg him to stay.

Certainly, Blair's position at the start of the year was precarious. He did not know what Lord Hutton would say about the death of David Kelly and the Conservatives were reviving under the leadership of an adversary he knew well enough to respect. It seems to have been around this time that he and Cherie decided to buy a house to move into when they moved out of Downing Street. We may find out whether that was part of a complex bluff to buy Brown's support, a precautionary measure or a provisional decision to go that was then reversed when Blair publishes his million-pound memoirs, which may not be for another five or six years yet.

The critical event of the year, then, and it was identified to me as such by one perceptive member of the PM's staff at the time, was Hutton's favourable verdict in January. "It means he's staying." Hutton was significant because it meant that Blair survived, but at the price of a further haemorrhage of middle-class Labour support. A Labour MP tells me that, after the Iraq war, there were two waves of emails of disillusion: one when the BBC seemed to take the rap for Hutton when ministers escaped, and another in October during the debate over the Black Watch deployment to central Iraq. But January 2004 also turned out to mark the high- water line of the Tory advance in the opinion polls - they hit an average of 35 per cent, kept it up until March, but then slipped back as what Americans would call Michael Howard's "negatives" rose.

Thus Blair ends the year as dominant a figure over the political landscape as ever, with no obvious impediment to his seeing through his declared ambition to outlast Thatcher. The Labour Party is conflicted, the liberal press in a state of perpetual outrage, the Tory press becoming more poisonous, and yet Blair has come through. His Chancellor retains all the power of the heir-apparent - he commands fearful respect from anyone with medium-term ambitions. And do not believe the arrogant Blairite talk of sacking him after the election - how can Blair say that Brown has been such a success as Chancellor that he wants him to take over the Foreign Office? But Brown has been brutally stripped of much authority over the here and now.

This was the year, then, when we had to come to terms with a new dispensation. One in which right-thinking opinion has turned permanently against Blair but in which he has turned out to be a more substantial and durable historical figure than could have been imagined.

I recall one occasion this year when I was being harangued by disillusioned ex-Labour supporters for his policy on Iraq. Being naturally diffident, I hesitated, giving my questioner the chance to go for the kill. "Mind you," she said. "I must give him credit for one thing. University fees. That really was necessary."

The vote on tuition fees in January, in which Blair saw his majority in the House of Commons cut from 161 to five, was a turning point that coincided with the Hutton report. Iraq will probably always be a contested legacy. His dream of a leadership role in Europe has died. So his reform plans for the public services - with tuition fees paving the way for a series of five-year plans over the summer - will, by default, be his lasting monument.

It will be a long time before they can be judged. So it is too early to ask where Blair stands in the league table of British prime ministers - just as it was too early for Clinton when his adviser Dick Morris told him that he regarded him as "borderline third-tier" in the pantheon of America's leaders. Last month a survey of academics in history and politics put Blair sixth among 20th-century prime ministers behind Attlee, Churchill, Lloyd George, Thatcher and Macmillan. It was a ranking - particularly that top slot - that said more about the biases of modern political history as a university subject than it did about the precise rankings of the big names. But the survey did make one point: that, having survived this year, Blair will be compared - for sheer longevity if nothing else - with some of the prime ministerial greats.