Anything is possible in politics. Prime ministers are capable of Lazarus-like recoveries even when the last rites have been read. Harold Wilson nearly did it in 1970 after the local election catastrophe of 1968. Margaret Thatcher won in 1983 after being hammered in the locals in 1981. But Wilson was helped by having an unappealing opponent in Ted Heath and Mrs Thatcher was fortunate enough to win the Falklands war in the interim.

Rather than resembling these two, however, Gordon Brown looks more like John Major in 1995. Mr Major, beset by sleaze, a severe loss of his government’s reputation for economic competence and an overwhelming appetite for change, won a mere quarter of the vote in the local elections and was sent packing with a landslide general election defeat two years later. And unlike his Tory predecessor, Mr Brown has not even been elected to office.

For David Cameron events could hardly look rosier. He might be tempted to sit back and let the premiership fall into his lap. But the Tory leader’s job is far from done and another test will come with the Crewe and Nantwich by-election later this month. It is, astonishingly, a quarter of a century since the Tories last won a by-election. Colin Rallings and Michael Thrasher, the pse-phologists, also point out that no party has won a general election without polling at least 40% of the vote in London. Last week the Conservatives were a little below that with 37%.

Mr Cameron’s challenge goes deeper than merely accumulating additional support in minor elections and opinion polls. There is a good chance he will continue to do that, given the worsening economic slowdown. The Bank of England has suggested that the first phase of the financial crisis may be over but it is concerned about the wider economic consequences. Alistair Darling’s budget prediction of a speedy recovery next year looks even more optimistic now than it did then. The government’s problems go beyond clumsy political manoeuvrings over tax rates. People feel squeezed by sharply rising food and energy prices, they feel overtaxed and they are rightly gloomy about what they expect to be a prolonged period of pain.

What Mr Cameron has to do is give people a sense of optimism and a positive reason for voting Tory. Any leader who finds himself prime minister solely on the back of a protest vote against the incumbent will soon struggle. Polls that show Labour in deep trouble also suggest there is limited enthusiasm for the Tories. Voters do not see the party as much more competent or honest than the government.

Mr Cameron has to generate a mood of excitement and enthusiasm. When Tony Blair became Labour leader in 1994 there was such enthusiasm and his victory in 1997 was seen, among the chattering classes, as the dawn of a new era. This is not just about policy; it is about capturing the mood and projecting excitement about change, as Barack Obama did for a while in America. The Tories plan a slow striptease over the next two years to unveil the policies that will form the basis of their manifesto. Voters, however, are less interested in the detail than in the tone.

Can Mr Cameron make people feel better about themselves? Can he make them yearn for a change of government? The kind of sparkle that Mr Blair had is rare and does not last forever once inside No 10. Nonetheless the Tory leader does have an easy manner and charisma, as his performance over the past two years has shown. And he has successfully positioned the party in the centre. Now that many people are thinking of him as the next prime minister, he has to show he has got something more.

The Conservatives are perhaps three quarters of the way to forming the next government. Their task is to turn a curmudgeonly attitude among the electorate into positive enthusiasm. After a great set of election results, that is the task Mr Cameron has to set himself.