A POLITICAL leader is someone who takes a party where they want to go. Tony Blair took Labour back to government for the first time in 18 years. Gordon Brown now looks to be in the irretrievable position of leading Labour out of government at the next general election. This weekend, Labour MPs and senior government ministers have already started asking themselves if they are prepared to follow the prime minister back into opposition. And if Brown is not at the helm, then who else is there?

After a dire month of failing poll ratings, a massacre in the English and Welsh local elections, the lost London mayoral contest to the Conservatives, and now the by-election slaughter in the once rock-solid Labour northern constituency of Crewe and Nantwich, which prompted David Cameron to confidently proclaim the death of New Labour, those around Brown are this weekend attempting what one minister told the Sunday Herald was "a painful and inevitable show of unity where there is none."

Labour's deputy leader, Harriet Harman, said the "vast majority" of Labour members were "solidly behind" Gordon Brown. Sources in Harman's office, however, admitted yesterday that no mini-survey had been conducted since the fall of Crewe and Nantwich and that the deputy leader was perhaps "assuming" the party was behind the PM.

Other assumptions at the senior end of the party indicate a growing acceptance that Brown has now passed the tipping point where he can recover well enough to lead Labour to even an honourable defeat at the next general election, rather than a slaughter on the same scale as Crewe, which would leave the parliamentary party with an unprecedented rump. Crewe's arithmetic, in which a 7000 Labour majority became an 8000 Tory majority, if repeated in a general election would mean the Conservative benches stuffed with 489 MPs and Labour with just 89. If anti-Labour voters in Scotland switched, not to the Tories, but to the Scottish Nationalists, Labour's woes could deepen further.

A meltdown on this scale won't happen, but what will worry Labour analysts most is that there is no statistical comfort zone to explain away the current crises. Those angry with Brown are not using the Greens or the Liberal Democrats to deposit their protest. Instead the switch is direct to the Tories, indicating that even in a northern seat once thought off-limits to David Cameron's appeal, the Crewe result is a nightmare outcome.

To put a stop to the night sweats and anxieties about the scale of the wipe-out awaiting them, Labour MPs appear to dividing themselves into two camps. One group wants to retain the belief that Brown can change both himself and the party's fortunes, and that come an election, voters will see Cameron as a risk. One MP said "Their arguments will be noisy, in public, and will insist they represent the true' voice of Labour."

Others are already working on silent backstage coups against Brown. The same MP said: "This is already taking place, and it will gain momentum as each day passes and each day shows nothing is changing."

Some MPs doubt the current PLP have it in them to stage a coup. The long-serving Austin Mitchell, MP for Grimsby, said: "This lot wouldn't know how to organise a coup even if the research department gave them a manual on how to do it." Mitchell said there was "no alternative" to Brown. Others don't buy that, saying leadership campaigns, however covertly, have already begun. Those in the frame and quietly trying to gauge their potential level of support include pensions secretary James Purnell, foreign secretary David Miliband and health secretary Alan Johnson. Education secretary Ed Balls and deputy leader Harriet Harman have done the opposite, contacting MPs and telling them of the dangers a contest would bring.

Analysing the TV appearances of leading contenders for Labour's crown, TNS Media Intelligence say that between May 6 and May 20 the favourite to succeed Brown, David Miliband, notched up 19 appearances on national channels. This was double his usual appearance rate. Ed Balls, in the same period, was on TV 13 times, nearly four times his usual rate. James Purnell also doubled his media profile.

Just a busy period for cabinet ministers? One MP described the recent mood of his parliamentary colleagues as "suicidal". He suggested that, unlike the slow march to inevitable defeat under Michael Foot in 1983, Labour, having been in government for over a decade, will do all they can to avoid being decimated at the next general election. But given Labour's internal rules on electing its leader, just what moves the coup plotters need to take, and what counter-moves the loyalists need to take to avoid a summer civil war, no one is sure.

For one Scottish MP there is no obvious way forward. "No-one knows how or when. No-one knows how much pressure it will take for Gordon to walk away and admit he can't cut it. No one knows what his departure would do, whether it will heal or open new wounds. No-one knows.

"But what most of the PLP privately accept is that Gordon isn't going to change much. Some of us knew that in 1994 when we voted for Tony. We knew it last year when he was elected unopposed. We still know it."

Margaret Beckett, regarded as one of the least effective foreign secretaries to hold the office, said Brown could change his course, and Labour could yet prove the electoral arithmetic wrong. Her comments this weekend are seen as the start of the public show of faith in Brown.

For others in no position to kick-start a coup, but who would like to see Brown go soon, if for no other reason than to give them a better chance of remaining at Westminster, a leadership contest designed to destroy Brown's authority and give him little hope of competing well against a substantial challenger is now the only way forward.

The former whip Graham Stringer insists it is the responsibility of senior members of the cabinet to mount this challenge. "Without that," says Stringer "we're heading for an electoral disaster at the next election, and I want to see Labour win."

Alan Simpson, one of the awkward squad who regularly troubled Blair's leadership, said voters in Crewe had shown they were fed up with "cheap politics" and gave Brown "until the end of the year to turn things round".

Some close to the PM believe that if he can get to the end of the year, he will make it through next year and still be in Number 10 to call an election in 2010. "This party won't change leader with less than a year left to polling. If there is a challenge, and I don't think there will be, then it will have to come before the party conference in October. Then Gordon Brown will call for unity and a common fight, and the party will respond positively," said one aide.

However, unlike the leadership contest called by John Major in June 1995, which was a relatively quick and effective way of silencing his critics, any formal challenge to Brown would last possibly into the spring of next year.

A fifth of Labour's 353 MPs would have to band together and back a challenger. A card vote at October's conference would have to support the challenger. A subsequent poll of Labour's electoral college - MPs, unions, and members - would be necessary before a formal vote was taken, plus an added period for an adequate campaign. By this time, with little prospect of global oil or food prices falling, the housing market still troubled and pay inflation pressures increasing, Brown's position as leader would become untenable. He would, at this stage, go rather than face the ignominy of becoming a PM defeated by his own party.

What a coup would be aimed to do is to fast-track this process. According to a former cabinet minister, the target would be Number 10. "To get it to accept its authority was gone; that Brown no longer had support from the senior ranks of his party. In effect, PM in name only."

For a former Number 10 aide, those inside Downing Street are already preparing for the "siege mentality" that might be needed to keep Brown in office long enough to mount a recovery. Another Whitehall aide close to Brown says they've known for some time what was coming. "Since 2004 and moving towards the 2005 general election, Labour's support has been falling. In 2005 the Tories got more votes in England than Labour did. And last year in Scotland, there wasn't a collapse of Labour's vote, but the Holyrood electoral system was sensitive enough to reflect a fall-off in our core support. That's why we lost control of the Scottish parliament. Now the local elections, London, Crewe - is it all Gordon Brown's fault? No. So removing Gordon Brown will change little."

That argument won't be enough to stop the plotting and the coming coup attempt. Brown is now regarded as another Jim Callaghan, taking the party towards defeat and another generation and more in opposition. Crewe was confirmation of what was known already.

The objective now is to take an existing silent, internal coup and bring it out into the open. Pressure will now fall on one of the Blairite big beasts to simply say the party cannot repeat the faults of the Foot era and hope the coded criticism is enough for Brown to go gracefully. That symbolic task is likely to fall to Charles Clarke or Alun Milburn outside the Cabinet. Inside the cabinet, rumours suggest Justice Secretary Jack Straw has been lobbied by some MPs to put party before anything else and warn Brown of the consequences of staying.

One MP, a former minister under Tony Blair, said "David Cameron announced the end of New Labour. Some of us accept that may indeed be the case. What no-one wants is the slow death of the Labour Party itself. Less than 100 Labour MPs on the opposition benches would be something that would take generations to recover from. What do we do? Doing nothing can't be our only option."