By Nick Assinder
Political correspondent, BBC News website
Only a couple of days ago the question was whether Labour's left could harm Gordon Brown - the answer is now a resounding "no" in the current leadership election.
Mr McDonnell struggled to get enough backers
It had all looked so promising on Monday for those who might want a contest when former minister Michael Meacher stepped aside and called on his supporters to back Campaign Group leader John McDonnell as the man to challenge Mr Brown for the leadership.
But, despite the fact they claimed to have enough support between them to get on to the ballot paper, Mr McDonnell failed to get close to the 45 nominations needed to go ahead and, on Wednesday evening, conceded defeat.
Clearly many of Mr Meacher's supporters were not as happy to switch to Mr McDonnell as the man himself was, and the chance of him getting 45 Labour MPs to back him by the Thursday 1230 BST deadline faded.
That this has happened will be of little surprise to those who know the left - and fellow travellers in the Labour Party have never been short of their own internal divisions and squabbles.
So the field has now been narrowed down to one - normally the sort of numbers Mr Brown is said to like best.
Although in this instance that might not necessarily be the case.
It was widely believed, with much justification, that when the chancellor said he wanted a contest he really meant it.
Not too serious a contest from, say, a staunch Blairite minister with the backing of Tony Blair.
But a contest with the sort of figure who represented old, left Labour and who could be soundly beaten, so giving Mr Brown a mandate and proving the old and, he would say election-losing, agenda was dead and buried.
Mr Brown said he would welcome a challenge
Such a contest and its inevitable outcome would have strengthened Mr Brown's hand considerably when dealing with left-wing rebels in future.
There was, of course, a danger that union and constituency party members might give the challenger a sizeable vote, so weakening Mr Brown's authority from day one.
But that relatively small risk was one Mr Brown was happy to take for the greater benefit of enhancing party democracy and underpinning his premiership.
There were certainly many in the Labour Party who want a contest for similar reasons and, simply, because they like the idea of having a say.
There had even been suggestions Mr Brown might "lend" some of his supporters to Mr McDonnell to ensure he got onto the ballot paper and allow the contest to go ahead.
However that would have been a dangerous tactic for a man who has put transparency and the ending of spin at the centre of his campaign, and the chancellor quickly dismissed it.
So we now look certain to have six weeks of what some are already dubbing the "phoney election", as Mr Brown travels the country, meeting voters, attending hustings and generally behaving as if he is not a foregone conclusion.
And any left-right or Brownite-Blairite battling will have to take place in the deputy leadership contest - a far less exciting prospect.