That the phrase "a week is a long time in politics" is so over-used does not mean it is without truth. Ed Miliband showed that in Manchester.
Ahead of the party's annual gathering, expectations were low. Yes, Labour rides high in the polls. But few would have put that down to Mr Miliband's leadership, which had been characterised as charisma-free and shackled to the union barons. His personal poll ratings were disastrous. One question, first posed in the same city two years ago, would not go away. Did Labour pick the right Miliband brother to take the fight to the Tories? David Miliband was still wearing the tag as the greatest leader the party never had on Monday night on the eve of his younger sibling's big conference address.
But, since Tuesday, something has changed.
Speaking without notes for an hour, a symbol of virility that saw him seldom trip over an "um" or an "er", is a remarkable feat of oratory. That is what the speech will be remembered for. But memory men do not necessarily make good Prime Ministers.
Politically, to lift a phrase beloved for moderate Tories – "One Nation" – and claim it as a Labour principle was as unexpected as it was audacious. Parking tanks on David Cameron's lawn was smart. The fight for the hallowed centre ground of politics – that bit that gets you elected – is officially on. He even hinted at no longer burying the party's head in the sand over deeply sensitive issues, including immigration control and public sector cuts.
The party faithful loved it. Exeter MP and former Cabinet minister Ben Bradshaw, a devout Blair-ite who backed David in the leadership campaign, hinted at this being the speech they have been waiting for him to make, swinging from humour to indignation and passion. Mr Bradshaw's delight summed up the general mood as the curtain came down on conference yesterday. Many probably didn't think he had it in him at all. His status within the party has been secured.
How the Conservative Party responds next week will be instructive. The tactic to date has been to let Red Ed get on with it, occasionally branding him as a hapless Wallace from Wallace and Gromit. They thought he was ineffectual. An electoral liability. Yet, in Manchester, where the rain is remorseless, he changed the political weather. An immediate poll bounce is the first headache it causes the coalition Government.
Policies will come, tucked under the One Nation umbrella, and for the first time the Ed Miliband centre-left vision is starting to emerge. Over to you, Mr Cameron.