The absence of trust. That's what's fuelling Labour's feuding. Gordon Brown and his supporters simply do not trust Tony Blair to arrange "a stable and orderly transition" (A-SOT) to the chancellor in the time needed to "renew" the party. Hence all the talk about the need for a public timetable.
This morning at his news conference the prime minister will seek to demolish the case for a timetable, arguing that it would be a gift to the Tories and Labour's enemies in the media. The Tories would present it as a "countdown to the end of New Labour" and some in the media as "only X days left for lame duck Blair". He will also, I suspect, try to be more conciliatory - reassuring his party that he backs Gordon to take over and sees the need for A-SOT.
It is perfectly possible that Tony Blair means what he says and will use the party conference, or his 10th anniversary in Number Ten, to announce his resignation and his backing for Gordon Brown. It's possible that his friends have to talk about staying on till 2008 to get that far.
It is equally possible that he doesn't trust Gordon Brown to continue his reforms, hopes that John Reid, or Alan Johnson, or even David Miliband may grow enough in their new roles to become plausible alternatives to Brown - who might shrink in popularity with the passage of time.
Of course if Blair and Brown were seen to be working together amicably and to the same agenda none of this would be a problem. There were ACAS-style talks between their two camps (led by Alastair Campbell and Ed Balls) at the beginning of the year. They ended when Charles Clarke was reported as talking about (he denies saying it) "a dual premiership". Ever since, the atmosphere between Blair & Brown has grown steadily worse.
If - and it's a big if - those talks can re-start and Gordon Brown looks happy, the much talked of letters calling for a timetable will probably never appear. If not, Labour MPs - whose survival, it's worth remembering, is at stake - may take matters into their own hands whatever they're told by Blair or Brown.