The unanimous verdict of the British media is that the last act of Tony Blair’s premiership is now being played out. The prime minister’s imminent political demise is awaited, anticipated, taken for granted by the very commentators who rose on his coat tails over the last decade.

Last week’s local elections, in which the Blair government did as badly as governments generally do in mid-term, set off a train of events. The subsequent Cabinet reshuffle, which resulted in the dismissal or demotion of several ministers, as reshuffles generally do, was predictably described as a “bloodbath.”

In fact, its most damaging feature was not the hiring or firing, but the continuation in office of Mr. Blair’s deputy, John Prescott, whose affair with a secretary has left him shorn of responsibilities but still enjoying the privileges of office. The preposterous Mr. Prescott’s adultery is now being investigated by Scotland Yard.

Far from calming the storm, however, the reshuffle provoked a new one. Now the worms of Westminster turned. The Parliamentary Labor Party descended into frenetic plotting, signaled by demands for the prime minister to set out a timetable for handing over power to his designated successor, the chancellor of the exchequer, Gordon Brown. Mr. Blair refused to give in to blackmail, pointing out that the machinery of government would be “paralyzed” during the transition.

But at a meeting of the Parliamentary Labor Party on Monday, the atmosphere was that of a lynch mob. Mr. Blair was repeatedly challenged to name the day that he would go. Back to the wall, he assured them that he would give his successor “ample” time to establish himself before the next general election.

He had given them an inch; they decided to take a mile. Mr. Blair’s answer was taken to mean that he will resign next year, less than halfway through his third term of office. Downing Street has neither confirmed nor denied this interpretation.

Mr. Brown, meanwhile, is willing to wound but afraid to strike. On Tuesday, he dropped a heavy hint that unless Mr. Blair went voluntarily he would be ejected by his party, just as Margaret Thatcher was. But Mr. Brown fears that voters would not thank him for ousting the man they re-elected just over a year ago. Not conscience, but calculation makes a coward of Gordon Brown.

It is, as I say, the unanimous verdict of the Westminster commentariat that this crisis is all about Mr. Blair. My own view is rather different. What we are witnessing is not the decline and fall of Tony Blair, but that of the Labor Party. Though it may mean the end of his tenure in Downing Street, the liberation of Mr. Blair from the shackles of his party is not the end of his career. In fact, it is a consummation devoutly to be wished.

If I am right, then the present crisis in British politics is not, as the conventional wisdom would have it, about the limits of leadership; it is about the pathology of parties – and of left-wing parties in particular.

What is a political party? One authority on this is Edmund Burke. In his “Thoughts on the Cause of the Present Discontents” (1770) Burke defines it thus: “Party is a body of men united, for promoting by their joint endeavours the national interest, upon some particular principle in which they are all agreed.”

Note that, for Burke, the national interest takes priority. The principle that gives the party its name – in this case, the Labor Party, which is supposed to represent working people – is clearly subordinate to the national interest. Otherwise you have not a party, but at best a faction, at worst a fifth column.

By this definition, many of Mr. Blair’s colleagues lost their right to call themselves a party when they began to oppose his conduct of the war on terror and the democratization of Iraq. They allowed their fundamentalist anti-Americanism – reinforced by assorted other prejudices – to override the national interest. Once British forces were committed, and even more after British civilians had been attacked on the streets of London last year, it was the duty of Labor legislators to support the prime minister, at least on the clear issue of principle that differentiated the government from pacifist Liberals and isolationist Tories. That the Labor rebels failed in their duty is not only a source of shame for them, but an infallible sign that their party is in an advanced state of decay. They are not rebels – they are a rabble.

The Labor Party, which has the collective memory of a lobotomized goldfish, has forgotten how it was rescued by Tony Blair from the depths of ignominy that it plumbed during the 11 years of Margaret Thatcher’ ascendancy. In Burke’s words, they are “men without popular confidence, public opinion, natural connexion, or mutual trust, invested with all the powers of government.”

Last week, I ran into Jose Maria Aznar, the former Spanish prime minister. This is the man who inspired Mr. Blair to limit his time in office. Mr. Aznar is still young and vigorous; he can now speak his mind more freely than during his eight years in office. Unlike Mr. Blair, Mr. Aznar can say openly that force may have to be used against Iran. So why does Mr. Blair soldier on? He has, after all, been in office for nine years already.

There is a one-word answer: Iran. Mr. Blair sees it as his mission to help President Bush to remove this third deadly threat (following Afghanistan and Iraq) to Israel and the West. The prime minister won’t quit until the job is done, simply because he doesn’t trust either Mr. Brown or anyone else to stand by Mr. Bush.

The Iranian crisis explains the most baffling aspect of the Cabinet reshuffle: the removal of Jack Straw as foreign secretary. Mr. Straw’s repeated public insistence that military action against Iran was “inconceivable” did not only irritate the White House: It irritated Mr. Straw’s boss, too – beyond endurance. The point about the new foreign secretary, Margaret Beckett, is not that she is the first woman to hold that post, but that she actually agrees with Mr. Blair on Iran.

Will Mr. Blair be allowed to fulfill his self-appointed mission? That depends on a desperate cabal of frauds, fiends, and fanatics. No, I don’t mean the Ahmadinejad regime in Teheran; I mean the Parliamentary Labor Party in London.