Chancellor Gordon Brown is unlikely to face a serious challenge in his expected bid to succeed Tony Blair as prime minister, the BBC has learned.
Gordon Brown is widely seen as favourite to succeed Tony Blair
A contest for the Labour leadership had seemed certain after Mr Blair announced in September that he would leave Downing Street within a year.
But sources now say it is becoming more likely that no heavyweight challenger to Mr Brown will emerge.
Left-wing MP John McDonnell has said he plans to stand in any contest.
'Almost certainly Gordon'
BBC political editor Nick Robinson said some senior Labour figures had come to believe Mr Brown was "simply unstoppable".
He added: "We've gone from 'anyone but Gordon' to the Labour Party thinking 'it's almost certainly Gordon'."
Mr McDonnell said he wanted to avoid a "coronation" of Mr Blair's successor and to give Labour a chance to decide its next leader.
There has been speculation that former Health Secretary Alan Milburn, Home Secretary John Reid and Education Secretary Alan Johnson - all Blairites - would stand, although none has made an announcement.
Mr Milburn is considered an "ultra-Blairite" and gave a series of speeches in September which were taken to indicate his willingness to lead the party.
Work and Pensions Secretary John Hutton has said there should be a contest, but refused to comment on whether he would stand.
Former Home Secretary Charles Clarke told BBC One's Question Time it was "very unlikely" he would run for Mr Blair's job.
He said he had always believed Mr Brown would make a "very good" prime minister, adding: "I can tell you what I expect to see. I expect to see Gordon Brown as the next leader of the Labour Party."
Candidates for the deputy leadership have been more forthcoming, with Hilary Benn, John Cruddas, Peter Hain and Harriet Harman all declaring their ambitions to take over when John Prescott leaves.