The Prime Minister wakes up to a political situation that could hardly be more precarious. The usual exercise in managing expectations should not obcure the bald numbers: Labour could only manage 20 per cent of the vote in the local elections. That is no less a calamity because 20 is a larger number than 18. Labour now controls no county councils at all.

It is quite common that, as political crises develop, we become inured to dreadful news. But the results that Labour is getting are far worse than the Government of John Major was recording at a similar point in the electoral cycle. It needs to be said with great clarity: these results are terminally disastrous for the Labour Party.

It is still an open question, however, whether the Labour Party wishes to draw any conclusions from this electoral rout about the future of its leader. Over the next 72 hours Gordon Brown will either be pressured, very much against his defiant will, out of office or he will cross a threshold that will ensure his survival. But, even at best, it will be no more than survival. He will have ensured only that he survives for the slow, painful death of his own repuation and that of the new Labour project that he helped to forge.

That makes today a critical day for the Labour Party. David Miliband, Alan Johnson, Jack Straw and Alistair Darling have made it plain that they do not think resignation is the method by which the Prime Minister should be forced out. They have 24 hours to decide whether they should instead act in concert to persuade him to do the honourable thing. Mr Miliband, in particular, needs to reflect on whether anything remains of his authority even if he ever does gain the leadership of his party.

Then the attention will pass to the Parliamentary Labour Party (PLP) to see if it can do what has so far seemed beyond the Cabinet - namely to look beyond the endless self-obsession that recalls the Conservative Party of the 1990s. MPs will have reflected on the European elections and what they portend for their futures. The meeting of the PLP this evening could then be the occasion on which the backbench rebels produce the names of the 71 MPs that would force a contest for the leadership.

But if neither the Cabinet nor the PLP chooses to move then there will be a moment in which we can do nothing else than pause to admire the extraordinary tenacity of the Prime Minister. And that one moment of admiration will then be followed by eleven months of living with the consequences of his survival. The Government has been quite unable to articulate a coherent domestic programme already. It will simply be impossible to achieve anything with a hobbled Prime Minister leading a Cabinet that he was unable to choose himself and which clings to him only for fear of something worse. As Lord Falconer of Thoroton says in The Times today, unity under Mr Brown is now impossible. A paralysed government is terrible for the nation. The poor leadership of the Labour Party is now throwing up serious questions about the quality of the nation's Government.

But this is now also about the future of Labour politics. The next few days could set the course of Labour politics for a generation. If the party decides to stick by Mr Brown it is likely he will lead them to a large defeat. The first years of opposition could be wasted in a war to assign blame. A much depleted parliamentary presence could shift significantly to the left, delaying the prospect of a return to power by a matter of years. A new leader might lessen the defeat and, at the same time, ensure a soft landing into opposition.

But the moment is upon them. The Cabinet risks being written off as a collection of cynics and cowards. It is almost too late.