By Nick Assinder
Political correspondent, BBC News website in Brighton
Gordon Brown's big speech, with its carefully-worded references to "New" and "renewed" Labour and its distinct Thatcherite overtones, is certain to intensify the leadership speculation already gripping this conference.
Brown will aim to persuade the party that he is Blair's natural successor
It may also, however, open up a wider debate amongst delegates over precisely what a Brown premiership would be like and where it would lead the Labour Party and the country.
There is a growing belief that what delegates in Brighton will witness this week is the start of that planned, "smooth transition of power" from outgoing prime minister Blair to new man Brown.
There are even those who believe the two men have come to an understanding which will see the chancellor helping secure Mr Blair's legacy of reform in return for an orderly, and swift takeover of power.
To that end Mr Brown will deliver a speech designed to, once again, prove he is the only natural successor to Tony Blair.
But he will also seek to unite the party behind a new, Brownite vision for the future which accepts the advances made by New Labour - he even uses the words which once used to stick in his throat - and even takes them further.
Thatcherite talk of creating a "home-owning, share-owning, asset-owning, wealth-owning democracy" may send shivers down the spines of old Labour, already showing signs of suspicion over his intentions once in power.
But his speech will also attempt to convince worried activists and trade unionists that he can be trusted not to betray them.
So, Mr Brown will go on to declare his vision is "not just for some, but for all, honouring our party's constitution - putting power, wealth and opportunity in the hands of the many and not just the few".
Brown is just as committed to reform as Tony Blair
"So when commentators tell you the next election will be old Labour versus new Conservatives, tell them the truth.
"The next election must and will be New Labour renewed against a Conservative party today incapable of renewal."
In a further attempt to reconcile New and Old Labour, he will add that the great Labour governments of the last century "were great because they were reforming, progressive governments that transformed Britain".
Mr Brown knows that he has two distinct audiences to satisfy with this overtly leadership-style speech.
First he has to reassure middle England voters that he is not about to abandon the reforms mapped out by Tony Blair and which saw them abandoning the Tories over the past eight years.
But he also has to persuade traditionalists in the party that he is still the man they believe him to be - the protector of the Labour soul.
Not just more Blairism
He has already been warned by some senior trades unionists that they expect something different from a Brown premiership, not just more Blairism.
Others, however, believe the chancellor is as much a creator of New Labour as the prime minister and is just as committed to reform, particularly of the public sector.
After Mr Brown's speech, delegates will be looking to the prime minister's performance later in the week for any signs of his intentions.
Meanwhile, there appears to be a gathering campaign aimed at ensuring the transition is indeed smooth, with senior Blairite figures like Tessa Jowell urging MPs not to spark a contest.
And many in Brighton believe the week will see an echo of the double-act performance between Blair and Brown which marked the last general election campaign.