The timing of Mr Blair's departure is less important than the context in which he leaves. If Gordon Brown and quite separately a disparate group of Labour MPs were to act in a way that makes the current political situation even more febrile, they would be the main victims of their own recklessness. Put bluntly, if a despairing Mr Blair leaves a party in turmoil, positioned on the part of the political spectrum that is perceived as opposing all reforms to the public sector, the main beneficiaries would be David Cameron and the Conservatives.
Mr Blair remains a perceptive reader of the political situation, the most observed of the observers. He would make a good political columnist of his own government, although his interpretations would be excessively generous. Astutely, he recognises the key question in British politics: who inherits the New Labour mantle when he goes, Gordon Brown's Labour Party or David Cameron's Conservatives?
If Labour vacates the terrain marked public service reform, Mr Blair knows that Mr Cameron would stride on to the free political space. Mr Blair notes that Mr Cameron is copying his political style and poses a second challenging question. If Mr Cameron recognises the style is a route to electoral victory, is it wise for the Labour Party to turn away from it?
A symptom of the current fin de siècle political mood is the circulation of wild rumours and speculation. In recent days, it has been suggested that Mr Blair and his entourage would prefer the Conservatives to win the next election rather than a Brown-led Labour Party. This is not true for several reasons, but most obviously of all because such an outcome would be highly damaging to Mr Blair's reputation as a leader.
He knows that Margaret Thatcher's reputation was fatally damaged by what happened to the Conservatives after she left and wants part of his legacy to be a still-thriving, election-winning Labour Party. As part of the process, he is watching David Cameron like a hawk and is ready to pounce when the next opposition leader is more clearly defined.
But he wants to pounce as the leader of a party that supports reforms to the public services. Most specifically, he looks to the support of Gordon Brown to get his reforms implemented. For one last time, he wants to work closely with Mr Brown on a series of policy issues. In Mr Blair's view, this would leave Mr Brown in the strongest of all positions as the next leader. The thorny reforms will have been implemented in the first half of the parliament leaving him free to focus on the next wave of issues relating to schools, hospitals and welfare.
In spite of persistent and real tensions, the broader aspirations of Mr Blair and Mr Brown coincide. Mr Brown does not want to inherit a traumatised and divided Labour Party. Some of his closest supporters have chided him for failing to launch a leadership bid against Mr Blair, most specifically during the summer before last. In effect, they accuse him of political cowardice, a fatal flaw for an aspirant leader.
They are wrong to do so. It would have been disastrous for Mr Brown to knife the Prime Minister, not least in the period shortly before the last general election. He would never have fully recovered his authority from an act of regicide. More importantly, the Labour Party would have been weaker. The Chancellor is a supreme strategist and knows with obvious frustration that the need for patience applies still.
The Chancellor would not have been human if he did not smile fleetingly at yesterday's appalling headlines for Mr Blair. But sticking to his Calvinistic tendencies, he will not have enjoyed himself too much. There is a good reason for this. Mr Brown will be damaged if it is perceived he has inherited a party that is in disarray and returning to a mythical old Labour past.
Contrary to the briefings of some Blairite ministers, the Chancellor is not one of the "forces of conservatism". At yesterday's Cabinet meeting, he gave an authoritative and detailed presentation of the economic challenges facing the Government. As well as the familiar themes relating to the global economy, he warned of inflationary pressures arising from the increases in public sector pay. He concluded unequivocally that reform of the public sector was required to ensure increases in productivity to accompany the generous, and in some cases too generous, pay awards. Mr Brown is no advocate of the status quo in the public sector and never has been.
He has deep disagreements with Mr Blair, to some extent articulated in public, about the impact of markets in some public services. But in terms of the leadership, he seeks passionately a smooth transition, waving off Mr Blair amicably as he voluntarily leaves the stage, his work complete.
Before then, Mr Blair must stress more persistently the dividing lines between him and the Conservative Party. He knows Mr Cameron's smart strategy is to decouple him from the Labour Party. The Labour Party, too, must be careful not to do Mr Cameron's work for him. Mr Brown must wait. He remains the only credible successor and the silly talk about the need to find a young alternative to Mr Cameron has ceased, at least for the time being.
These are tempestuous times. One government insider suggests that the Blunkett resignation will make waves for longer than usual because it is part of a larger picture, the attempt to drive through unpopular reforms, the rise of Mr Cameron and uncertainty about Mr Blair's departure. A cabinet minister reflects on how at times in the 1980s Labour was in a battle for third place and suggests nothing can be taken for granted now.
Yet in spite of the real and unavoidable tensions, the three pivotal elements to the story are bound together. Mr Blair wants to leave behind a Labour Party capable of defeating the Conservatives. Mr Brown wants to inherit a Labour Party that is formidably strong. Most Labour MPs want Mr Brown to flourish as leader and not stagger pathetically to an election defeat. There is just about a way through the current tempest, but if Labour lapses into persistent strife, it risks losing the next election.
We know Mr Blair is going. It is the Labour Party that must rise to the challenge of winning a fourth term.