Conventional wisdom is a poor guide to the future.

At the end of the 20th century, few would have thought that the coming decade would see the election of a black US president, a power-sharing deal between Sinn Fein and the Democratic Unionists, and the nationalisation of some of Britain’s biggest banks.

Yet, even in the face of such unexpected recent events, we still cling to the notion of political ­inevitability. It is now widely regarded as a certainty that Labour will lose the next election, with the Tories on course to form a large majority in the Commons.

A combination of sleaze, exhaustion and economic meltdown are said to have finished off the Labour government. Gordon Brown is seen as a political corpse. The only question to be decided at the polls, it seems, is the scale of his defeat.

But once more, conventional wisdom could be wrong. Labour might look doomed at the moment, in the febrile atmosphere created by the expenses scandal, but the picture could be very different next summer, if the worst of the charlatans have been kicked out of the cabinet and an economic recovery is under way. Moreover, a number of features of the structure of our political system are likely to benefit Labour in the run-up to the next general election.

Even now, in the midst of crisis, it is not all gloom for the government. On 21 May, Labour won a council by-election in Salford, the seat of the discredited Communities Secretary, Hazel Blears, whose conduct over her home allowances has been condemned by Brown as “totally unacceptable”.

Given Blears’s role at the centre of ­Scamalot, the Labour vote in Salford might have been expected to collapse dramatically, but it held up. Meanwhile, the Tory vote dropped, as the party’s candidate was overtaken by both Ukip and the BNP.

Indeed, the Conservatives have not been doing nearly as well in council by-elections as they should be for a party on the verge of government. In one poll at the start of May, in the Rossmere ward of Hartlepool, the Labour vote actually went up, while the Tories were consigned to fifth place.

The national opinion polls are, of course, bleak for the government, but then they also were at the time of the European elections in 2004, a year before Blair’s third triumph. The average Tory lead of 10-12 per cent in recent months might look healthy, but, in truth, if replicated at a general election, it would be barely enough to win. After three successive landslide defeats, the task facing the Conservatives at the next election is daunting.

Taking account of boundary changes, they have to gain at least 112 seats to form an overall majority in the Commons. That would require a 7.1 swing, the equivalent of an 11 per cent lead over Labour in the national British vote, far beyond the scale of anything achieved by a previous Tory opposition.

It is a remarkable historical fact that since the end of the Victorian age, the Conservatives have only once turned out a government which possessed a working majority in parliament. That occurred in 1970, when Ted Heath – defying conventional wisdom and the polls – defeated Harold Wilson’s government, though even then the swing was 4.7 per cent, significantly lower than that needed by Cameron.

Every other Tory victory since 1900 has been against a dying coalition or Labour government which had lost its majority, or never held one.

Nor do all of Cameron’s target seats appear to be in fertile territory for Conservatism. On the list are places such as Keighley, Dewsbury, Derby North, Rossendale and Dumfries and Galloway. It is difficult to envisage all of them turning blue, especially if the general election next year takes place against a backdrop of improving economic news.

When the Chancellor, Alistair Darling, announced in the pre-Budget report last year that recovery could start in the autumn of 2009, he was derided for his prediction. But this could be the reality. Such a recovery would not address the appalling state of the public finances, with levels of national indebtedness far worse than at any time in our history.

Yet it is unlikely that the ­question of the national debt will be a deciding factor at the next election. People will be much more influenced by their own job prospects and personal income. Most homeowners lucky enough to be in work have not suffered too badly in this recession because of the dramatic fall in ­interest rates. There is no sign that rates will increase over the coming year.

By next year, the impact of the expenses scandal and the Smeargate fiasco may have faded. All the opinion polls over the past two years demonstrate that Brown’s ratings improve when economic questions predominate. Again in defiance of conventional wisdom, the Prime Minister’s strange political personality might assist in Labour’s revival in the months before the next election.

His combination of bullying, indecisiveness, cowardice and lack of vision have rightly made him despised by large sections of the public. Yet his strongest trait, his aggressive partisanship, currently a vice, could in future become an asset to Labour.

Every decision Brown makes is dictated, not by the national interests, but by his narrow determination to outflank the Tories. This has led him to absurdities like his notorious pledge of “British jobs for British workers”, but some of his negative campaigning may prove more fruitful.

The stark warnings about “Tory cuts” will be pounded home relentlessly over the next 12 months, and this message is bound to find a receptive audience among two key groups of voters: public-sector workers and welfare claimants, both of whom have done comparatively well from Labour rule. Together, these two groups have more than 12 million votes.

Brown’s partisanship will ensure that every aspect of the political system is ruthlessly exploited to Labour’s advantage. Labour’s turnout will be heavily boosted by postal voting, which, as a series of fraud scandals have proved, is open to corruption by agents and activists. One judge, presiding in 2005 over a case involving a municipal postal voting fraud in Birmingham, said the scale of abuses by six local Labour candidates would have “disgraced a banana republic”.

Indeed, the Labour government cynically introduced postal voting on demand without safeguards in 2000 precisely because it knew the party would be the big winner from such a flawed method. At the 2005 election, 6.5 million people voted by post. The figure will be even higher in 2010 and the misrepresentation even worse.

Similarly, the government will indulge in a wealth of feel-good propaganda over the next year, dressing up pro-Labour publicity as consultation and information exercises. Already the government is by far the biggest advertiser in the country, with the Central Office of Information holding a budget of £400m. Marketing by other pro-Labour public-sector organisations will be added to the political spin.

We can expect schools, hospitals, regeneration projects, community groups and Sure Start centres to start putting up signs at their entrances explaining how much the government has recently invested in their sites. In the same way, the £2.3bn regional development agencies, which the Tories have pledged to abolish, will have everything to gain by launching expensive billboard campaigns telling us about wonderful economic success ­stories in their regions.

Conventional wisdom holds that there will be a big anti-incumbency vote at the next election because of public disillusionment over the current House of Commons. But the opposite may be true. Sitting MPs have two great advantages.

First, their casework means that they have had supportive contact with thousands of voters. The huge increase in staffing allowances in the past decade means that they can often employ two or three assistants in the constituency working on behalf of their local public.

In the 1980s, Chris Smith managed to hang on to a wafer-thin majority in Islington South partly through his assiduity in handling an epic volume of casework, most of them housing issues that should really have been dealt with by local councillors. His winning slogan in the 1987 election was: “Everyone knows somebody who’s been helped by Chris Smith.”

This will be a theme taken up by a host of Labour MPs in 2010. The second advantage is the £10,000-a-year communications allowance, which enables incumbents to spread the gospel of their devotion to their constituents through glossy newsletters.

The changing demography of Britain will also help Labour. The phenomenal increase in mass immigration over the past decade has not only transformed the make-up of our urban society, but has undoubtedly been a significant boon to Labour. All studies show that the overwhelming majority of voters in migrant communities tend to vote Labour. Eighty per cent of black voters back the party and at least 60 per cent of Asians.

Tellingly, many of the highest concentrations of ethnic minorities are in the swaths of marginal seats in outer London, the West Midlands and South Yorkshire. According to the campaign group Operation Black Vote, as many as 70 marginals could be decided by black and Asian voters.

Harriet Harman’s Equality Bill, with its legalisation of positive discrimination in favour of minorities, will be a strong campaigning point for Labour. The influence of the ethnic vote on Labour thinking was graphically revealed in the diary of Chris Mullin, where in January 2004, he lamented how little the government had done to tackle immigration abuses. “We’ve barely touched the rackets that surround arranged marriages. What mugs we are.” Then he added a comment to the effect that there was the difficulty that “at least 20 Labour seats, including Jack Straw’s, depend on Asian votes”.

Brown’s campaign in 2010 may be desperate, cynical, even deceitful, but that does not mean it will not work. Negative campaigning has worked in the past, most famously in 1992 when the Tories’ demolition of “Labour’s tax bombshell” led to John Major’s victory and one of the biggest upsets in history. A discredited government in the fifth year of its third term can stil