By Nick Assinder
Political correspondent, BBC News website
So that is it - Gordon Brown will be Britain's next prime minister without facing a challenge.
As a result, politics has now entered a strange, six-week period of limbo with plenty of sound and fury but little of real significance taking place.
Mr Blair's off, but Mr Brown's got to wait. Will limbo be the result?
The outgoing prime minister, Tony Blair, is still in charge - as both Downing Street and Mr Brown are eager to stress.
But he is engaged in a long "legacy tour" - much of it outside the UK - and is concentrating all his energies on attempting to write, or even re-write, his own history in Downing Street and push Iraq down the agenda.
The incoming prime minister will now be attending hustings and visiting constituencies around the country in a "phoney election campaign" the outcome of which is a foregone conclusion.
But although he might take power until 27 June, he will have regular discussions with the prime minister on policy and specifically the two looming international summits - even though he will not be attending either.
The danger is that, while all this is going on, government business will be, to all intents and purposes, on hold as civil servants, backbench MPs and even the opposition parties wait to see the whites of the eyes of the new premier.
The chancellor is working to avoid that by agreeing to have talks on future policy with cabinet secretary Sir Gus O'Donnell, in addition to giving clear hints about big changes ahead.
Iraq still threatens to overshadow all else
These changes include a Constitutional Reform Bill which is likely to include a new ministerial code and greater scrutiny powers for MPs.
He says he intends to create a "new government with new priorities", suggesting it would be a big mistake to assume the current Blair agenda will remain untouched.
He has even hinted at a new approach to Iraq, going as close to an admission of errors as any minister so far done by saying he will seek to restore trust in foreign policy.
But he will now take a step back while he travels the country trying to "listen and learn" ahead of working to "earn trust".
While Mr Brown prepares for office, the task for Tony Blair is to write his legacy while attempting to show he really is still running the country as if nothing has changed.
On the domestic front he has already had his moment in Belfast at the launch of the new Stormont assembly - and helping to bring peace to Northern Ireland will undoubtedly stand as one of his greatest, if not the greatest, of his achievements.
Mr Blair sees the Northern Ireland peace deal as big part of his legacy
Then there is the publication of policy reviews on the role of the state and the family and two White Papers on planning and, something that promises to be highly-controversial, the security of Britain's energy supply and the possible role for nuclear power.
There will also be specific events centred on health and education, designed to emphasise the positive, while addressing the perceived contradiction that individuals will often declare their local hospital or school is great while, at the same time, believing the education system or NHS as a whole is failing.
On foreign policy, one word hangs over everything else - Iraq.
Mr Blair has probably come to accept that he can do nothing now to change the public's verdict on that war. So he will instead concentrate on pushing other "legacy issues" up the agenda.
The Blair years
First there is the world tour - accompanied by documentary-makers and, it is believed, a novelist - taking in Washington, Europe, Africa and the Middle East.
The aim will be to emphasis the positives of the Blair years - particularly successful military interventions like Sierra Leone and Kosovo, aid packages and environmental and poverty campaigns.
Nuclear power plans will prove controversial
Then there are those crucial G8 and EU summits next month, at which he will want to be seen to be leading moves towards new deals on climate change and Europe's future.
Mr Blair has kicked it off with another visit his closest ally President George W Bush.
It is all planned to end with a triumphant and forward-looking exit from No 10 - not a tearful re-run of Margaret Thatcher's departure.
What all this activity amounts to is an attempt to stick as closely as possible to the procession outlined in that leaked Downing Street memo that last year talked of the prime minister leaving "with the crowds wanting more" and as "the star who won't even play that last encore".
Things may not be quite as euphoric as the writers of that memo hoped. Indeed, there are those in the Labour Party who believe he has outstayed his welcome.
And it is impossible to ignore the fact that this is not the way he wanted to go - effectively forced out early by the attempted coup last year.
Still, he is determined to offer some positives to set against that huge negative - a difficult task as the situation in Iraq always threatens to erupt.
And, in any case, six weeks is a terribly short time in which to write the history of a decade in Downing Street.