Victory, John F. Kennedy memorably intoned, “has a thousand fathers but defeat is an orphan”. The Prime Minister this morning finds himself a political orphan as never before in his career. While local elections occur every year, there are some of them - once a decade perhaps - which are far more than an assortment of numbers and the ill-formed expression of a national mood dominated by the disgruntled, but not really an indicator of something bigger. The contests held on Thursday are in a different league entirely. They are genuinely seismic in their implication. If Gordon Brown is eventually defeated in his bid to take Labour to a fourth term, then this is the moment which historians will determine marked the beginning of the end of his spell as Prime Minister. These local elections also mean that the ultimate battle is unlikely to occur before May 6, 2010.

If that general election had been held on May 1 then the Labour Party would have been slaughtered. To describe the results of this poll as “bad” or “disappointing” is a serious understatement. They were absolutely awful. Never in the post-war era has the party sunk to around a quarter or less of the projected national vote and the official prediction of a loss of 200 council seats, made to lower expectations and cushion the defeat, was in the end wildly optimistic. Labour's meltdown occurred everywhere - not just in the south or suburbia but in the crucial North West of England, the West Midlands and in places in Wales where in the past it made more sense to weigh the Labour vote rather than bother counting it. There were no crumbs of comfort available.

What message should Mr Brown take from this astonishing rejection? He said yesterday that he would “listen and lead”. That is half-right. If by listening he engaged in a wave of short-term policy reversals and stunts then he is done for. It is the “lead” element that he must focus upon.

For the response of a Prime Minister after a hammering is usually to assert that they will “go on governing”. In practice, however, what they actually do is “go on politicking”. Strategy is sidelined for tactics in the desperate but invariably doomed search for electoral salvation. Mr Brown should eschew all talk of reshuffles or new policy wheezes deliberately designed to seduce voters or alternative slogans with which to try to bring down David Cameron in the eyes of the country. The experience of the 10p tax band debacle and the botched reposte to the Tory inheritance tax move should surely have sent their warning.

What Mr Brown should do instead may seem counter-intuitive (especially to him) but it is in his own best interests. He should work on the assumptions that it will be very difficult indeed for Labour to win a fourth term in power but, paradoxically, it would be no less improbable for any rival to unseat him. He must in the immediate weeks ahead concentrate on the economy, but more broadly swear a vow truly to concentrate on the “long-term” measures to improve Britain which he is fond of talking about but often puts to one side when the equivalent of Baldrick's “I have a cunning plan” in Blackadder is offered to him by one of his inner circle. He should look to encourage business, pursue genuine reform in the public services through the rapid expansion of the city academy programme and should want to overhaul the welfare budget. He should aim his sights at Britain in 2020, not May 6, 2010.

Such an approach would have real virtues. At worst, it would mean that after three years as the Prime Minister, Mr Brown, even if he lost by a sizeable margin, would have achieved more in Downing Street than John Major, for instance, managed in twice as long a tenure. At best, the Prime Minister might find that the electorate has time for sober and responsible administration.

The dilemma for Mr Cameron is different. His biggest challenge is to understand the distinction between “time for a change” and “time for an alternative” and be the second of these options. It would be comparatively easy for him to keep exploiting the Government's troubles, make his policy prescriptions as general as he can get away with and to be inoffensive in the hope of attracting voters.

This might deliver him victory but it would not bequeath much of a mandate. It is also an approach which might not withstand the scrutiny of an election campaign, particularly if the Prime Minister does devote himself to the long-term. It is not enough for Mr Cameron to calculate that the public has heard his message about the modernisation of the Conservative Party and walked down to the polling station to express approval. The reality is that people have half-heard his pitch and about one-quarter understood it. This is entirely excusable and there are many inside the parliamentary Conservative Party itself and by no means just on the backbenches who have a semi-detached relationship to his modernisation. Mr Cameron remains short of assembling a convincing team that might take Whitehall by storm and implement a coherent agenda right across it.

The Conservative leader has almost done too well in these elections. The spotlight will be put on him as a Prime Minister in-waiting and on his party as government in-waiting as never before. Hazy statements such as insisting that “bottom-up” reform will occur within the public services will not pass muster. He is in a strong position but should not sit on that strength nor appease those in his ranks who regard modernisation as but a respray job for their traditional automobile.

The same applies to Nick Clegg and the Liberal Democrats. These elections will have come as something of a relief to him and his supporters. It would not have been a surprise if the Liberal Democrat proportion of the estimated national vote had fallen quite sharply this year as 2004 had been a memorable outing for the party as it milked opposition to the Iraq intervention. The narrative of this poll could have been that both Mr Brown and Mr Clegg endured losses on their first proper outing in front of the electorate. That the numbers have instead been mildly positive for the Liberal Democrats will allow Mr Clegg a most welcome breathing space and the chance to assess what it is that he argues to the country. The role of the leader of a third party is constrained and reactive. Mr Clegg should conclude, nevertheless, that the old Lib Dem line of “a plague on both your houses” will not do at the hustings. If Mr Cameron sticks with “time for a change” and does not embrace “time for an alternative” then Mr Clegg has to be ready to be that alternative.

Britain is destined for the politics of the long haul. This could be a disspiriting 24 months with echoes of the 1993-1997 period when a Government which was manifestly exhausted and dying on its feet refused to expire its last and be gone. If so, Mr Brown, Mr Cameron, Mr Clegg and the rest of us are in for immense frustration. It can, perhaps, be a much more positive experience if the Prime Minister puts the big issues before the petty calculations, Mr Cameron appreciates his need to demonstrate additional substance while Mr Clegg drags his colleagues from their collective comfort zone. The pessimists will inevitably dismiss any prospect of such a benign scenario. Who, though, wants to be ruled by pessimists?