A senior figure at Downing Street put it concisely: "One day, Tony will come in and say, 'the bad news is that I am going. And the bad news is that you are going too'."
Even Blair aides, few of whom would survive the transition to Gordon Brown, know that the moment is getting nearer. They also know that Mr Blair's desire to surprise us by announcing he is quitting when we are not expecting it is going to be much harder to achieve.
Some Blair acolytes claim the opinion polls showing Labour six or eight points behind the Tories will bring rebellious Labour MPs to their senses. I suspect they will draw a different conclusion: that Mr Blair should be on his bike faster than David Cameron.
To be fair, most people around the Prime Minister know the ground has shifted beneath his feet. He expected the Brownites to shake the tree after the local elections to see if Mr Blair would fall off his branch. He didn't expect Mr Brown to do it himself by calling for "renewal".
Nor did Mr Blair expect mainstream Labour MPs to call on him to reach agreement with Mr Brown on a timetable for the "stable and orderly transition" he promised a year ago. When they joined forces with the Brownites at a meeting of the Parliamentary Labour Party (PLP) on Monday, the Prime Minister realised he was in deep trouble.
He tried to get out of it by promising his successor "ample time" to settle in before the next general election. But that wasn't enough. The nadir of a terrible week came the following morning when Mr Brown said on GMTV: "Remember when Margaret Thatcher left, it was unstable, it was disorderly and it was undignified." One Blair ally replied: "That was a declaration of war, given what Tony had promised the PLP. Gordon was publicly threatening Tony with the same fate as Thatcher."
A day earlier, at his monthly press conference, Mr Blair had dismissed parallels between his plight and the fall of Baroness Thatcher in 1990 in her third term. Now it didn't feel so different after all.
The fury in No 10 was palpable. "Brown has got his finger on the nuclear button and - this time - he keeps pressing it," one Blair adviser said. The metaphor was apt: in previous bouts of the "TB-GBs," the Chancellor and Prime Minister pulled back from the brink because they faced mutually assured destruction - "Mad" for short.
The shifting sands were visible at Prime Minister's Questions on Wednesday. I have never seen such a sea of blank faces behind Mr Blair. He was under an attack from David Cameron over the Government's paralysis but Labour MPs were in no mood to lob him friendly questions. They sat sullen and silent. They didn't even laugh at his jokes.
On Thursday night there was finally some relief for Mr Blair when he and Mr Brown agreed the outlines of a deal on pensions. At least a few headlines about policy suggested that the Government was not totally paralysed. But even then their aides were spinning rival versions of the pensions settlement.
The Brownites may keep shaking the tree unless Mr Blair gives more than nods and winks suggesting that he might quit in 2007. Mr Brown feels he has been betrayed by Mr Blair at least twice before and wants an agreement to be witnessed by others.
Mr Blair believes that such a "private" deal would soon become public and he would not become so much a lame duck as a dead duck. He is happy to give private assurances. But he has not agreed to hold the talks with "senior colleagues" that the Chancellor announced on GMTV.
Mr Blair should now agree to talks in return for Mr Brown calling off his attack dogs. Otherwise the Blair legacy and Brown inheritance will be a divided party seen by the voters as obsessed with their internal battles.
Enough damage has already been done. According to YouGov, 83 per cent of people regard Labour as divided, and only 6 per cent view it as a united party. In contrast, the Tories are seen as united by 44 per cent and divided by 27 per cent. Yesterday a Populus poll for the BBC's Daily Politics programme found that 67 per cent of people regard Labour as more interested in internal squabbles than the issues that affect their daily lives.
Perhaps Labour's big beasts could afford the odd spat when there was no real alternative. Those days are over. The Tories' 40 per cent share of the vote in the council elections makes it important for Labour to keep their eyes on the ball and not to kick lumps out of each other.
If they carry on as they are, neither the Blair or Brown camps will win the power struggle which has raged between them since the death of John Smith, 12 years ago yesterday. The only winner will be David Cameron. In 2009.Reuse content