Mr Blair will quit his job within months

The thin chord that binds political ambition to popular acceptance has been broken

I don't know how serious the Prime Minister's health problems are. They may be more threatening than Number 10 would have us believe. Or they may be trivial. But I do know that if I were Tony Blair I'd take these intimations of mortality as the occasion to get out of the job. Indeed I'm willing to bet that by Easter he may well have done so.

Never, comes the reply from those who know him. Blair's appetite for power remains undiminished and he would hate to go when things were running against him. At this point, he has every prospect of winning the next election to give him a record third term, while to go now would be to risk being accused of running for cover.

Fair enough. In the dreams that all politicians are prey to, Blair would prefer to go on a high, with the Northern Ireland parliament restored at Stormont, Iraq set upon a path of democracy and Britain playing a major part in a newly enlarged Europe - perhaps even preparing to join the euro. But that is not the scenario the Prime Minister is facing nor, given his heart condition, can he necessarily wait until circumstances make it attractive to go.

It's not the heart condition itself. But for any man or woman heart troubles, like signs of cancer, are warnings that you are mortal. Asked on a recent Desert Islands Discs why he had decided to retire from the British ambassadorship to the US only months before the Iraq invasion, Sir Christopher Meyer said that a check-up revealed heart fibrillations. Not serious enough in itself to propel retirement but sufficient to encourage a rebalancing of lifestyle. (Sir Christopher is now head of the press Complaints Commission - hardly a relaxed retirement job.)

Looking around, as Blair must, what does he now see? Nothing which seems likely to force his resignation, that is true. The Hutton inquiry report, if the general expectation of fellow lawyers is anything to go by, will be far more interested in process than individual blame, and will be too tightly drawn to get anywhere near the Prime Minister's office, although it may criticise some of the informality of its decision-making. Iraq is not going well, but there are now plans for early democracy which might allow Britain to start pulling back its forces. The parliamentary party is troublesome, but it's still difficult to see the revolt over tuition fees reaching the point of forcing the Prime Minister out. According to all the psephologists, it would take a swing of unprecedented scale to make him lose the next election.

But then there is nothing that gives much hope for better days. Iraq may take years to get right and finally bring the Prime Minister little credit for doing so. European politics are getting more gloomy by the day, so that it is now difficult to see a euro-referendum within the next Parliament, never mind this. The days of an unimpeded majority are over as the Tories regain their vigour under a new leadership. The all-important relationship between Prime Minister and Chancellor will get more fractious the nearer the election looms and the more frustrated Gordon Brown becomes at an ever receding horizon of hope.

Above all, Blair faces an electorate that has grown disillusioned with the tone of youthful optimism and deep concern which stood him so well in the early years. It's not that they have completely turned against him. They still quite like the boyishness and they don't instinctively sense that he is either corrupt or nasty. It's just that they no longer believe him or his promises. That thin chord that binds political ambition to popular acceptance has been broken, and it's almost impossible see how it can be reworked.

In the world outside Britain, in contrast, Blair's standing remains high. Despite his involvement in the Iraqi invasion - a decision that tends to be put down to loyalty to America rather than perfidious Albion ambitions - the British Prime Minister continues to enjoy high recognition and warm feelings around the globe. In America he is regarded as a statesman of real stature.

Should he wish to give up here, there would be no shortage of offers abroad and no shortage of cash. The US lecture circuit alone could bring him several million dollars a year. In time all sorts of jobs - President of Europe, Secretary General of the United Nations, chairman of global companies - could come his way. Look to the examples of Henry Kissinger, Giscard d'Estaing, Romano Prodi, Jimmy Carter and, of course, Bill Clinton. The end of domestic office does not mean the end of position and prestige, whatever the opprobrium you have suffered at the point of leaving.

Tony Blair is not a man who retires to his study to contemplate his own soul or the dark heart of the world around him. He is a politician who tends to take decisions as they come from a broad sense of conviction. But he is man who likes to be ahead of the game, to feel that he understands a situation quicker and better than most.

On the one side is trudging on to an election where you are asking the electorate to vote you in for a term you know that you will not fulfil. On the other side is a better, and better-respected, life outside British domestic politics. Which would you choose if you'd just suffered twice in a month from a heart scare?

a.hamilton@independent.co.uk