A week after the event, almost everyone seems to agree that Gordon Brown’s last Budget was a competent exercise in economic management, but a serious political blunder.

This may seem no great disaster to Mr Brown. He would much rather be seen as a good economic manager and a bad politician than the other way round. He feels he has plenty of time to recover from a typical mid-term wobble in the opinion polls.

That, at least, seems to be what Mr Brown tells himself when he lies awake at night worrying about his political future — as he surely must do now and then. It is a reassuring story: as long as the economy stays healthy, wages and house prices keep rising, while unemployment, mortgage rates and inflation all remain far below their levels in the 1980s and 1990s, surely the voters’ top priority will be to keep the prosperity going. However much they complain about spin and dishonesty and lack of vision, however much they may rail against all politics and politicians, people will vote for the devil they know. In a nutshell the Chancellor’s reassuring story comes down to the refrain made famous by Bill Clinton’s election campaign in 1992: “It’s the economy, stupid.”

Whatever the question, Mr Clinton as a candidate decided to give the same answer: he would fix the American economy and everything else would then fall into place. Such economic determinism seems even more appealing for Mr Brown today.

Britain’s economic advance this decade, from the poorest to the second-richest country among the main advanced economies, is a far more remarkable transformation than anything that happened in America before or after the Clinton period — and Mr Brown, as the longest continuously serving Chancellor in history, deserves substantial credit for this economic renaissance. Moreover, any attempt by the Tories to divert political arguments at the next election away from the prosperous state of the economy would lead on to battlefields where public trust in Conservative policies was even weaker — especially education and health.

Unfortunately for Mr Brown, all these reassuring arguments are spurious for simple reasons. First, because economics was never as decisive in politics as implied by the Clinton slogan and will, in fact, become less important with every year that goes by. Secondly, because Mr Brown is wrong to assume that health and education will be the main non-economic issues in the next election.

The limited role of economics in determining electoral outcomes is obvious from recent British history. While the changes of government in 1974 and 1979 were certainly triggered by economic crises, the country also voted for a change of government in 1964, 1970 and 1997, despite conditions of prosperity and strong economic growth. On the other hand, the economic crises of 1980-81 and 1990-91 were followed by election victories for the incumbent government, even though most voters still believed that the economy was in recession — and held the government responsible — when they went to the polls.

The examples of 1983 and 1992 illustrate one obvious flaw in the “economic determinism” thesis. If the Opposition is led badly, as it was by Michael Foot in 1983, it has no chance of being elected, even when the economy is in dire straits. And even when presented with a half-credible alternative, as they were by Neil Kinnock in 1992, a recent economic crisis can frighten voters, making them reluctant to vote for change. Conditions of relative prosperity, by contrast, can make voters bolder and more inclined to a flutter on untested opposition leaders, as they did in 1964, 1970 and 1997.

Assuming that Britain’s good economic performance continues until the end of the decade, which it almost certainly will, this may be just the situation in 2009-10. After 17 or 18 years of uninterrupted economic growth, voters will take prosperity for granted and will pay very little attention to economic issues, especially if the tax, spending and business policies of Labour and Tories are very similar, as they now are. Political attention will inevitably shift to other issues. Mr Brown thinks this shift would nonetheless be to his advantage, because public suspicions of Tory policies on health and education are so deeply ingrained. But this seems to be his second fallacy.

By aping new Labour’s health and education policies, David Cameron may not have shown much vision or imagination, but he has probably neutralised the Tories’ longstanding electoral disadvantage in these fields. The result is that “public services” could turn out to be as irrelevant as economics in the next general election. What, then, will be left for the public to vote on? The kneejerk answer from most British politicians and commentators is “nothing”.

Having spent the entire postwar era arguing about taxes, interest rates, comprehensive education and the NHS, they tend to assume that these are the only important issues in politics. Yet this is demonstrably untrue. Anyone who opens a newspaper or talks to ordinary people instead of politicians must realise that foreign policy is a much bigger issue today than economics and that crime is a greater worry than the future of the NHS. Moreover, a broader perspective shows that the dominance of economics and public services in British politics was a historical temporary aberration, rather than the norm. Before the 1930s, there was little serious disagreement between political parties on macroeconomic management, while health did not even exist as an issue for national politics before 1945.

The historical norm, looking not only at Britain but also at other democracies in America and Europe, has been for governments to win or lose on the basis of issues that most British politicians still consider marginal: constitutional reform, criminal justice, civil liberties and philosophical issues such as the content of education, rather than its structure. An even more crucial determinant of political success throughout most of recorded history has been foreign policy and, above all, the decision to wage or refrain from war.

Such issues tend to be dismissed as electorally marginal by politicians who learnt their trade in the left-right ideological battles of the second half of the 20th century. But war, crime and constitutional issues are likely to dominate British public debate in the years ahead.

Any politician who wants to win the next general election will have reverse the old Clinton slogan: we are now in world where “It’s not the economy, stupid”. As for Gordon Brown, he must recognise that good economic management is no longer a sufficient qualification for national leadership. Now he must prove he is also a good politician.

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