It has been the longest leadership campaign in history - or at least it feels that way - but yesterday David Cameron was elected Tory leader. Nick Morrison looks at the challenge facing him if he is to transform his party and challenge for the keys at Number 10.

FOR 100 years it was one of the world's most exclusive clubs, with a membership of just one. But the last five years have seen Austen Chamberlain joined by William Hague, Iain Duncan Smith and Michael Howard. Now the question is whether David Cameron's name will be added to the roll of shame, leaders of the modern Conservative Party who have never become prime minister.

Throughout the 20th century, the Tory Party regarded itself as the natural party of government, holding office for all but 29 of its first 97 years.

But recent history has been less favourable. The wrong end of two landslides, and a third barely-more creditable defeat, have left the party staring into an abyss with just one fear - that it might never form a government again.

It is a terrifying prospect for a party which has become used to office, and which tolerated opposition only as a brief and sometimes necessary breather from the rigours of running the country. And it is against this background that Cameron has emerged as a potential saviour.

The youngest of a once-crowded field, he stood out both for his lack of political baggage and his determination to champion a fresh approach for a venerable party. Under him, he said, the Conservatives would be compassionate, they would have a caring face, they would share the proceeds of wealth, they would reflect the make-up of society rather than being at odds with it.

This message was enough to get him elected, but it is now that his problems will start, according to Nick Randall, lecturer in British politics at Newcastle University. For all his rhetoric, it is now crunch time for Cameron. The Tory Party has still not lost the taste for treachery it acquired in the defenestration of Margaret Thatcher, and it is once Cameron's position on policy becomes clear that the sniping will begin

'I'm still no clearer on what compassionate Conservatism means," says Dr Randall. "One of the things he needs to do is put some flesh on the bones, and that is when he will start upsetting people. It could mean not being hostile to public services, but other Conservative leaders have tried to get that across as well and failed.

"And the difficulty is that if there is a compassionate Conservatism, it is to the left of where they have been. It means soft-pedalling on the traditional meat to right-wingers: asylum, immigration and law and order, but adding social policy, which has largely been absent in the last three elections."

But if Cameron does try and take his party to new ground, he has another complication: Labour is already there. "One problem is the absence of clear blue water between them and New Labour. Unless compassionate Conservatism has got something unique and distinctive that we have all not heard about, it is going to be difficult to differentiate themselves," says Dr Randall.

Without clear policy differences, Cameron will have to rely on his character for electoral advantage. And while the appeal of a youthful and vigorous leader may get him so far, it may not be enough to dislodge a government which will probably have been in power for 12 years at the next election.

As his predecessors have found, it is hard to oust a government which has presided over a successful economy, and although Gordon Brown's pre-Budget report on Monday held signs of turbulence, it seems a long way short of doing for Labour's reputation for competence what Black Wednesday did for the Tories, or the Winter of Discontent did for Labour 27 years ago.

Cameron will be able to draw on a new generation of MPs, unsullied by previous association with government and an asset largely denied to the three previous leaders, particularly Hague. But although he may have more going for him than any of them, he is still vulnerable to the charge of inexperience. Conversely, he has time to develop an agenda before the next election, and may yet frighten Labour.

As the economy starts to splutter, and voters tire of Labour in government, Cameron may be able to lift the veil which has shrouded successive oppositions in anonymity for the best part of a decade. As the fresh alternative to Gordon Brown, he may be an appealing prospect for the electors.

His challenge is to convert those people who are now in the habit of voting Labour, including those who rebelled last time over Iraq knowing they could protest with little chance of letting in the Tories. For if Cameron is unable to go beyond the core Conservative vote, he could be consigning his party to history.

"He has to offer something to people who have stuck with Labour since 1997, to break that link or provide something that will bring them back," says Dr Randall. "This is really the last chance: if the Conservatives don't get in next time, or they're not the largest party, there is a danger of a permanent Labour-Liberal coalition.

"To some extent it is make or break. He is going to have to drag the party up from the 34-35 per cent in the polls it has been since 1992, and find some way of being a more potential prime minister than any Conservative leader since 1997, otherwise his party may be doomed."