All the talk of a post-Blair era may not be as appealing just now to the ambitious prime-minister-in-waiting, the Chancellor Gordon Brown, as many suggest, writes Philip Stephens.
For a decade there have been two immutable truths in British politics. Gordon Brown has always believed that he was cheated out of the Labour leadership after the death of John Smith; and, almost from the moment of Tony Blair's coronation, the Chancellor has been impatient to push him aside.
So we must imagine that Mr Brown is more than content with all the latest speculation that the prize, at last, is within his grasp. Politics, though, is never that simple. Extraordinary as it may seem, he may secretly be hoping that Mr Blair hangs on.
What passes for conventional wisdom in the frenzied atmosphere at Westminster says otherwise. One former minister, who can claim a long and close friendship with the Chancellor, has been heard to say that it is now certain that his man will be crowned before the summer break. Other Brownites are behaving as if they have already stepped into their ministerial limousines.
All this is brushed aside as the usual summer froth by the present occupant of 10 Downing Street. Mr Blair is in no mood to step down. Those who say he may simply walk away from the chaos of Iraq have forgotten how much store prime ministers set by the judgment of history. Mr Blair does not want to be another Anthony Eden.
Still more intriguing, though, is the possibility that the Chancellor himself may be equivocal about an early handover. Just as Mr Blair concerns himself with his legacy, Mr Brown must be thinking hard about the condition of any inheritance.
Even in tranquil times the Chancellor would not find the transition to No 10 as easy as his acolytes presume. Charles Clarke, John Reid or both would make a fight of any leadership contest. For all that some Conservative newspapers are quick to press his claim, the Chancellor is smart enough to know they would be fair-weather friends. Mr Brown would make a much easier target for the Tories than Mr Blair.
In part, the Chancellor has himself to blame. The quest for easy applause in his own party has seen him project an image to the world beyond that of a politician far to the left of Mr Blair.
I have given up counting the number of times I have heard people say that, at heart, Mr Brown is a red-blooded socialist. His speech to last autumn's party conference, an attack on Mr Blair's modernism, is often cited as proof. So, too, are the politics of his principal cheerleaders at Westminster. Clare Short, George Mudie, Doug Henderson and Nick Brown are rarely seen as voices of moderation.
The truth is complicated. Mr Brown's instincts and outlook are indeed more egalitarian than those of the Prime Minister; hence the frequent arguments about public service reform, with Mr Blair championing excellence over the Chancellor's preference for equity.
Nor is Mr Brown's Scottish Presbyterianism naturally in tune with the ungodly materialism of the aspirant classes of middle England. It is no accident that the Chancellor spends as little time as possible south of the border.
On the other hand, his conversion to orthodox economics is real and his attachment to incentives for entrepreneurs almost as strong as his attachment to help for the poor. His arguments with Mr Blair have often been as much about personal positioning as ideology.
There is a separate question, though, about temperament. Mr Blair thrives on the unpredictable nature of life in No 10. He has the barrister's confidence to make instant decisions on issues about which his knowledge is necessarily limited.
Mr Brown's outward self-assurance masks inner insecurities. Once formed, his convictions are unshakeable, but the deliberative process is long and secretive. In the Treasury, many decisions go untaken. That is not a luxury allowed prime ministers. Nor is Mr Brown's habit of relying on the advice of the tiniest coterie of aides. Prime ministers need to make friends of political rivals.
None of these is an insurmountable hurdle, but my guess is that they make Mr Brown think hard about the circumstances in which he would take over.
Last autumn he threw caution to the winds, openly agitating against Mr Blair. There must be a temptation to do the same now. After all, if the Prime Minister survives, there is no telling how long he might stay; and Mr Brown knows his own premiership will not be complete until he has won a general election.
Yet, for now at least, the Chancellor is standing on the sidelines. That must be because he realises that almost any circumstances that demanded the Prime Minister's departure would weigh heavily on his successor. The violence in Iraq will not end because Labour chooses a new leader.
A party that had defenestrated Mr Blair, of course, would demand his replacement break with President Bush and withdraw British troops from Iraq. I cannot imagine that Mr Brown, an instinctive Atlanticist, would find that palatable. Nor would it win the applause of that nice newspaper proprietor and welcome guest at the Treasury, Rupert Murdoch.
In the many ups and downs of the turbulent relationship between Mr Blair and Mr Brown there has been one constant: a resentful but mutual recognition that, for all the rivalry, their fortunes are bound together more closely than either would like.