Following the unprecedented debacle - never before has the party suffered two landslide defeats in succession - he had little option but to go. The rump parliamentary party can now exhaust itself further, making the all but impossible choice between Kenneth Clarke and Michael Portillo. Yet it is far from clear that installing either man in Mr Hague's place will make much difference. For the Tories' real problem is structural, not personal. Even with the Younger Pitt as leader they would probably lose the next election. And maybe the one after that too.

Most of us regard the close rivalry between Labour and the Conservatives as a perennial feature of British political life. We therefore assume that, just as Labour eventually bounced back after the nadir of 1983, so the Tories too will sooner or later get their act together and return to power. Certainly, they have a record of recovering from adversity. Back in 1832, their share of total votes slumped to 29 per cent - but three years later it was up again to 43 per cent and by 1842 they were back in power. Similarly, their wipe-out in 1906, which saw their number of seats in the House of Commons fall from 402 to 156, was only temporary: after the 1910 election they had only two seats fewer than the Liberals and during the first world war they quietly took over, albeit with David Lloyd George as front man.

Moreover, the Tories have been extraordinarily good at holding on to power once they have won it back. The period 1979-97 can now be understood as one of four protracted periods of Tory dominance, the others being 1886-1906, 1931-45 and 1951-64. As they blinked glumly at their tele- vision sets on Thursday night, die-hard loyalists will doubtless have reassured themselves: we'll bounce back again.

But can they really recover from this historic double whammy (once a favourite Tory phrase)? I am not so sure.

The fate of today's Conservative party may well be to repeat that of the Liberal party in the 1920s. Despite having won a Blair-like victory in 1906, the Liberals slumped to the narrowest of victories in 1910 and never governed again. Chronic divisions within their leadership, the nature of the electoral system and a crumbling of their local organisation condemned them to an apparently irreversible collapse.

Above all, their ideological clothes were stolen: under Stanley Baldwin the Conservatives mutated into the party of business and sound finance, while under Ramsay MacDonald the Labour party was able to appropriate the old Liberal radicalism.

Something similar may be happening to today's Tories. The party's leading figures have been waging internecine war over Europe for the better part of three decades. The rank and file have aged alarmingly. The party's financial dependence on a handful of maverick millionaires is far from healthy.

Structurally, too, the Tories have long been in a weaker position than election results have suggested. In most elections (32 out of 43 since the Great Reform Act), the Tories have won a larger proportion of seats in the Commons than their share of the popular vote. The odd years out since 1900 were 1906, 1910 (both elections), 1945, 1966 and 1997, and now 2001. As in 1997, Liberal Democrat and Labour gains in key areas have spelt disproportionate losses in terms of Tory seats: in other words, the first-past-the-post system is now working against the Tories.

That said, the root of the Tory decline is that, like the Liberals in the 1920s, they have had their best clothes stolen. So successfully has Tony Blair rebranded New Labour as the party of economic competence that Labour now leads the Tories by 25 per cent in the opinion polls on this issue. What ensured this second Labour term more than anything else was the absence of the kind of economic crisis that has done for them in the past (in 1929, for example, and again in the mid-1970s).

But it is not just a matter of competence, or good luck. So fiscally conservative has Gordon Brown been as chancellor - paying off the national debt, no less - that the Liberal Democrats have emerged as the leftwing alternative to Labour. On defence it has been the same story. With the end of the cold war the Tories lost the stick with which Labour could most easily be beaten: their apparent reluctance to stand up to the Soviet nuclear threat. In the 1990s, however, British foreign policy was confronted by a very different question: what to do when people in the Balkans started killing one another? Contemplating Bosnia, John Major dithered. Faced with Kosovo, Mr Blair went to war.

Even on law and order the Tories have been squeezed. On election day, The Daily Telegraph carried a heart-warming story of a West Country candidate - an burly ex-Territorial Army farmer - who interrupted his canvassing to rugby-tackle a thief. A model of Tory values - but for the fact that he was a Labour candidate.

So comprehensively has their wardrobe been raided that the Tories are left wearing nothing but their rather tatty, non-Calvin-Klein underwear. By calling for harsher treatment of "bogus" asylum-seekers, Mr Hague sounded xenophobic. By offering tax cuts without proportionate spending cuts, he sounded fraudulent.

Even more contemptible - and this was one reason they did not get my vote - the Tories simply chickened out of making the authentically Conservative case that the government has been undermining the country's time-honoured institutions. The calculation, presumably, was that most voters could not care less about the union with Scotland, the hereditary peerage or, for that matter, fox-hunting.

The only remaining idea Mr Hague ventured to wave at the voters was opposition to the single currency. The striking thing here, as in 1997, has been the abject failure of this tactic to mobilise voters. Though they may not be enthusiastic about the single currency, the electorate plainly loathes the Conservative party far more than it loves the pound sterling. Indeed, the more opposition to joining economic and monetary union is identified with the Tories, the more likely the government is to win a referendum on the issue.

For the foreseeable future, the Conservatives' preoccupation will yet again be with choosing a leader. To recover any of the ideological territory captured by Labour, they would probably stand a better chance with the pragmatic and affable Ken Clarke; but Mr Clarke's enthusiasm for Europe makes the flamboyant Michael Portillo the more likely victor, given the possible imminence of a euro referendum.

There is a very small chance that Mr Portillo could prove to be the Disraeli of his time. They do indeed have much in common, not least that risky flamboyance. Disraeli succeeded partly because of his flair in restoring a divided and apparently discredited party to power after a commensurate debacle and a long period in the wilderness. Maybe Mr Portillo could do the same. But it must be said that the odds are heavily against it. The author is professor of political and financial history at Oxford University and author of The Cash Nexus: Money and Power in the Modern World (Penguin)