The biggest secret in British politics is coming out. Tony Blair, it seems, is not sure that Gordon Brown is the right man to take over from him.
It is one conclusion we can draw at the end of a momentous week in which the strained "TB-GB" relationship finally snapped. "Tony doesn't regard Gordon as his best successor," one Blairite minister told me yesterday. "He sees him as his only successor, which is different."
I have watched the "TB-GB rollercoaster" closely for 20 years. Occasionally, I felt as though I was riding on it, and have been accused by both men of being in the other's camp when all I was doing was observing events.
When I spoke a few months ago to a private gathering of ministers, several asked me what I thought would happen about the succession. I predicted that the Prime Minister and Chancellor would - just about - keep the show on the road and achieve a transition without too much blood being spilt.
I wouldn't make the same forecast after the past week. The carpet is already seeping with blood and I suspect there is more to come.
Mr Blair is furious with Mr Brown at what he is convinced was an attempted coup by the Chancellor's supporters. Even if he didn't start it, the Blair camp believes he could have halted it on Wednesday, and prevented the resignation of eight junior members of the Government, if he had spoken up for Mr Blair.
While Mr Brown supported Mr Blair when he broke his silence on Thursday, the Prime Minister pointedly declined to praise or endorse the Chancellor during his emotional apology for the turmoil of the past week.
The hints about the tensions between them have been there over the years. The biggest clue came when Mr Blair told last year's Labour conference: "Every time I've ever introduced a reform in government, I wish in retrospect I had gone further." It was a barbed reference to differences with Mr Brown which prevented him going further.
One Blair ally claims that the Chancellor "could have been Prime Minister by now" if only he had thrown all his weight behind Mr Blair's reform programme.
According to this version of events, Mr Blair wrote a private letter to Mr Brown in January, promising to quit around his 10th anniversary in Downing Street in May next year and offering to let his broad timetable become known. In return, he wanted the Chancellor's full support for the policies he wanted to push through in the meantime.
Mr Brown reacted positively and there seemed to the makings of a "stable and orderly transition". But the deal fell at the first hurdle when the two men clashed over pensions reform because the Chancellor had grave doubts about the cost of the blueprint drawn up by Lord Turner of Ecchinswell.
The Blair camp claims Mr Brown scuppered their emerging agreement on the transition. The Brownites say it would have been irresponsible for their man to sign off a package he believed the country could not afford, and to give Mr Blair a blank cheque to push through anything just to speed up his departure.
When the friends-turned-rivals held two tense meetings on Wednesday, Mr Brown sought Mr Blair's endorsement as his successor - in part to discourage a "stop Gordon" candidate from running against him in the leadership election. The Chancellor also sought a bigger say over government decisions before Mr Blair departs. But Mr Blair apparently dismissed what allies called a demand for a "dual premiership" and "co-decision making" which amounted to a Brown veto.
One minister admits there has been a "conspiracy of silence" in the Blair camp over Mr Blair's real views about Mr Brown because they were so incendiary. That period seems to be over.
But allowing such doubts to surface is playing with fire. The Blair camp has no viable alternative candidate to oppose Mr Brown. It hoped David Miliband might run, but he has backed the Chancellor. Alan Johnson might stand for both deputy and leader but is still relatively inexperienced. John Reid is tough but Scottish like Mr Brown and lacks strong support among MPs, as does Alan Milburn.
Charles Clarke is heavyweight enough to run but would be in a much stronger position if he had remained in the Cabinet. Perhaps Mr Blair regrets sacking him as Home Secretary over the foreign prisoners fiasco and maybe Mr Clarke regrets not accepting another cabinet post.
Brown supporters saw Mr Clarke's ferocious assault as part of a "stop Gordon" campaign. Blairites insist there is no co-ordinated campaign to stop anyone but say they will call for a debate about ideas and policies.
In his current mood, I suspect Mr Blair's inclination is to endorse nobody as his successor. That will be seen as giving tacit support to the anti-Brown brigade, a campaign without a leader.
It is a high-risk strategy, especially as Mr Blair apparently thinks Mr Brown is certain to win. The file marked "Brown" that Tory officials keep at their headquarters must be bulging with examples of what his Labour "colleagues" say about him. Brown allies fear that the attacks on him from his own side will only help one person: David Cameron.
In the dark days of opposition, when Mr Blair and Mr Brown were friends rather than rivals, they were among the first Labour figures to learn the lesson that a party obsessed with internal squabbling will alienate the voters. Last week, both men seemed to have forgotten it.Reuse content