With the drugs question refusing to go away, teams of Sunday newspaper reporters have spent the last week delving into the shadow Education Secretary's background.
They have been contacting former colleagues at Oxford University, Conservative Central Office and Carlton Communications, where he was corporate communications director. They are rumoured to be tracking down Eton schoolmates.
New urgency has been added to their search by Mr Cameron's refusal to tell BBC1's Question Time whether he had taken class A drugs, and his confirmation yesterday that a close relative was battling heroin addiction.
The Cameron team are anxiously awaiting tomorrow's headlines. New allegations of drug-taking would force him into a damage limitation exercise before the first round of voting on Tuesday.
Mr Cameron is understood to have given interviews to two Sunday newpapers. Some allies have urged candour, but he is unlikely to break his pledge never to discuss private matters.
One supporter insists: "Colleagues are interested not so much in whether he experimented with drugs, but how he is handling this situation.
"His great weakness is his lack of experience, what he would be like under fire. If he manages this situation, it will be a major boost for him."
It is not a view shared by all of Mr Cameron's allies. They fear that if he makes an unambiguous statement on drugs, he could be haunted by the subject, as was Michael Portillo, when he spoke of homosexual experiences.
If he does not, they worry that the subject could haunt him all the way to early December, when Tory members choose their leader.
A new bitterness has crept into the contest in recent days, with Cameron supporters accusing rival camps of innuendo and anonymous telephone calls. Senior allies of rivals David Davis, Liam Fox and Kenneth Clarke, have shown no compunction in raising the subject of drugs with political journalists. One MP says: "There are certain swivel-eyed right-wingers talking to the press and trying to destroy David Cameron."
Cameron supporters also claim rival candidates have done just enough to keep the pot boiling. Mr Davis told reporters this week that he never commented on fellow Tories, but added, unprompted, that he had never taken drugs.
And in a final unsolicited comment to a husting meeting in Westminster, Mr Clarke said: "I haven't taken cocaine, if that's what you're going to ask."
At the moment, with 34 declared backers, and private promises of support, Mr Cameron looks sure to be on the short-list of two leadership candidates presented to the 300,000 Tory members.
Will they tolerate youthful indiscretions by a man decades younger than most of them? The young pretender could still be doomed by an older generation's conservatism.