By Nick Assinder
Political correspondent, BBC News website
The fact that Gordon Brown has infuriated the Labour left with his support for Trident will not lose him any sleep.
Brown is straying off Treasury brief
Indeed, since Neil Kinnock's day, Labour leaders have worked on the basis that if they are upsetting the lefties they are probably doing something right.
Mr Brown was given the clearest sign of that - and the fact he may now lose their support in any leadership contest - from former minister Clare Short.
She declared: "That is the end. There is no chance of uniting around Gordon Brown for a progressive consensus. This is Iraq-plus".
She added there was no point supporting another leader who was, on defence and a series of other policies, simply going to continue a Blairite agenda.
But Mr Brown, like others before him, believes he is sticking to policies that appeal to the wider electorate - the people who choose prime ministers - and the greater Labour movement - the people who elect party leaders. He can, he undoubtedly believes, live without the likes of Clare Short, despite her previous support.
And it is undoubtedly that wider audience he has been addressing on Trident and with previous remarks about sticking to a Blairite agenda on public service reform, law and order, nuclear power and pay restraint, for example.
As an aside, the chancellor is also determined to maintain good relations with the White House which any unilateral abandonment of the nuclear deterrent would put under severe strain.
None of this will, or should, have come as any surprise to the left of the Labour Party.
It was, after all, Tony Blair, Peter Mandelson and Gordon Brown who built New Labour and, while the chancellor can speak the language of old Labour and trades unionists, he is as New as they come.
Mr Brown is also eager to dismiss claims from the opposition, and even some in the Blair camp, that he is a constant "roadblock to reform".
It also seems there may be an "understanding" between Mr Brown and Mr Blair that, if the smooth transition of power is to remain smooth, the chancellor will do nothing to threaten what the prime minister believes is his legacy.
Trident has been symbolic for left
Mr Brown's packed agenda of forthcoming, non-treasury engagements has led to renewed speculation that we are already witnessing that transition of power.
Whether that speculation is right or not, Mr Brown's persistent Blairism seems certain to ensure that there is a contest for the leadership, whenever it comes, with the left putting up their own candidate.
The chancellor may welcome that, as victory over such an opponent would add legitimacy to his premiership.
But a greater danger lurks in these waters.
If there is a leadership contest, as many now believe is inevitable, it may not only be the left who run a candidate.
There is a current of thought that, once Tony Blair goes, the last thing the Labour movement or the electorate will want is more of the same.
Some see beginnings of handover of power
There may be some worries on the Labour benches over whether Mr Brown is a fresh enough face to answer the threat coming from the apparently revitalised, Cameron-led Tories.
It all makes Gordon Brown's task pretty clear. He has to hold the Blairite line while, at the same time, managing to look fresh and "renewed", and offering something distinctly different from both his predecessor and the new Tories.
So, no trouble there then.