It's been more of a marathon than a sprint, but the race for the Conservative leadership finally gets to the voting stages today. Nick Morrison looks at who is in with a chance - and asks whether it matters who leads the Tory Party.

ONE is a scion of privilege: Eton and Oxford, married to the daughter of a baronet, a country sports enthusiast. The other is the son of a single parent, grandson of a Jarrow marcher, brought up on a council estate and with a taste for extreme sports.

But it is the toff who speaks the language of inclusion, of reaching out to people generally neglected by the party of wealth and rank. It is the commoner, the one who has made his way through determination and ability, to whom such language comes awkwardly.

Nothing is straightforward in the race for the Conservative leadership. It now seems likely that it will be the two Davids, Cameron the toff, Davis the common man, who will go into the ballot of party members next month. But as MPs make their choice today in the first round of voting to whittle the field down to the final two, it is against a backdrop which has changed dramatically in the last few weeks.

When Kenneth Clarke launched his leadership bid at the end of August, the former Chancellor's juggernaut seemed unstoppable. A Clarke-Davis run-off was the only game in town, and the rest were making up the numbers, or laying down a marker for future contests.

Now, Clarke is struggling to avoid the ignominy of being dumped at the first hurdle. Davis still looks a certainty for the members' ballot, but his standing among the party faithful seems less sure than it was. It is Cameron, the young grandee, who has what George W Bush calls the "Big Mo", momentum.

All of this is apparently the result of a successful campaign launch and then a vigorous and well-received speech at the party conference. Cameron is the man of the moment to such an extent that even his refusal to answer questions over whether he ever used drugs has not derailed his train.

"No-one thought Cameron would have taken off in the way he has. He just happened to click at the Tory conference," says Martin Farr, politics lecturer at Newcastle University. "It is very similar to Tony Blair, who became leader of the Labour Party because of the precise moment John Smith died. Had he died six months earlier, Gordon Brown would have been leader."

Cameron's initial appeal is his youth. At 39, he is the youngest in the field, and if he wins he would be the youngest Tory leader since... William Hague. But if the precedent is not entirely encouraging, Cameron has clear advantages over the Yorkshire wunderkind.

"When William Hague became leader in 1997 it was with the intention of having a young leader, more in tune with modern Britain," says Dr Farr. "He went to the Notting Hill Carnival and drank from coconuts, but it all felt rather forced.

"He was clearly the wrong person. He was, and is, a political anorak, who struck most people as being quite weird, but Cameron happens to have the manner and appeal of a normal person, even though he is from a privileged background, and he can engage with younger people."

His refusal to answer the drugs question, in effect a tacit admission that he did smoke cannabis at university, will help strengthen his image as an ordinary bloke, although it may not go down that well with the blue rinse brigade who will vote in the final run-off. But the very fact it has not disqualified him already is a measure of how far the party has come in the eight years since Michael Portillo's admission of homosexual relationships in his past scuppered his leadership ambitions.

As well as Cameron's emergence, the two most striking features of the leadership campaign have been how Clarke's campaign seems to have spluttered to a standstill, and how Davis has lost his position as front-runner.

Clarke's difficulties can be explained in part by Cameron's rise as a credible and charismatic candidate of the left of the party. Although Cameron is more of a Thatcherite than his language often suggests, he has provided a standard around which the One Nation Tories can unite. In contrast, it is easy to see Clarke as yesterday's man, a candidate with little fresh or new to offer.

The parallels with Labour in the 1990s are clear. Clarke has the same "one last heave" appeal as John Smith, but there are those who feel this will not be enough, just as Tony Blair believed it would not be enough in 1992, and only a radical overhaul of the party would propel it into power.

As for Davis, his position as darling of the right faltered at the party conference, due both to his own lacklustre speech, and a barnstormer from the other right-winger in the contest, Liam Fox.

By pushing all the right buttons, of flag, patriotism and hostility to Europe, Fox shoe-horned himself into the hearts of die-hard Thatcherites. While it is unlikely to be enough to take him into the run-off, and he is still favourite to be eliminated first, it did take some of the lustre away from Davis. And if it does come down to a choice between the two Davids, although with an electorate as contrary as the Conservative Parliamentary Party this is far from certain, then Davis's safety-first speech may come back to haunt him, according to Dr Farr.

"I think Cameron will represent something which is optimistic and fresh, and that may capitalise on the doubts people have about Davis, which is that he is essentially quite macho, his appeal is too narrow and he proved to be leaden at conference," he says.

"A lot of people thought he was Iain Duncan Smith with hair, and Blair would run rings around him. Cameron represents to the Conservatives what Blair was to Labour."

Although Labour still has a healthy majority, the gap between sitting MP and second place in many of its seats is barely into four figures. And with Gordon Brown in 10 Downing Street and the economy faltering, the Tories have their best chance of success since 1987, given that John Major triumphed against the odds in 1992.

"There is much more to play for now than in previous elections," says Dr Farr. "Whoever won the leadership in 1997 and 2001 knew they were in for a hiding, but this time there is a chance they could win.

"I think Labour will be terrified of Cameron because they have no answer to him in so many areas. He will appeal to people who used to vote Conservative but now vote Labour, and Labour is getting to the stage the Tories were at in the early 1990s.

"It is inevitable that they will be presented as tired and having nothing to offer, and against that there will be a youthful and charismatic leader who is bringing his party to the centre. This is the Tory dream: replicating the success of New Labour."

Although Cameron has been an MP for only four years, as opposed to 11 for Tony Blair when he became Labour leader, he would be able to counter accusations of inexperience with the charge that only two Labour ministers had been in government prior to 1997.

There is still some way to go, but for all Clarke's unchallenged position as the "big beast" in the leadership campaign, it may be Cameron who strikes most fear into the hearts of his opponents. It is Cameron who will be able to offer something fresh and new, and while these may be superficial characteristics, they are still ones that appeal to voters.

And for all that he is a toff, Cameron is the one with the common touch. With a disabled son and another child on the way, it is his appeal which may prove most compelling.

It may be David Davis who was in the Territorial SAS, but his caution at the party conference, in contrast to Cameron's gamble, may come to haunt him. It may be that Who Dares Wins after all.

"Cameron consciously gambled and Davis consciously played safe, and the consequences should be lessons about when it is necessary to take a risk," says Dr Farr. "Cameron had nothing to lose, and I can see why Davis did what he did, but it would have provided many people who were sceptical about him with the evidence that he doesn't really have what it takes.

"He is an effective backroom operator, but doesn't have the X factor, whereas Cameron came across as a breath of fresh air. It is a great lesson that many great political careers have been built on moments of accepting risk, and Cameron took the risk."