Henry Chu / Los Angeles Times

VATICAN CITY — Deep inside a safe in the papal apartment lies a top-secret report — for his holiness’ eyes only — that has become the most-talked-about document in Rome.

Written by three elderly cardinals, the dossier delves into the most damaging security breach inside the Vatican in living memory: the recent leak of private papers belonging to Pope Benedict XVI. The pontiff commissioned the senior prelates to find out how such a major lapse could have occurred and why.

Where the fingers point — already a matter of fevered conjecture in the Italian press — could become a factor in the selection of the next pope. Even though the 115 cardinals who will choose a new pontiff are not being allowed to read the confidential file, what they believe to be in it could color their decision.

Speculation over the dossier’s potentially explosive contents is just part of the politicking that is likely to go into the heavily veiled process of picking a new leader for the world’s 1.1 billion Roman Catholics.

That process in effect started earlier than usual this time because of Benedict’s surprise announcement of his intention to step down from office rather than let death remove him from it. The advance notice of a vacancy on the throne of St. Peter means that papal hopefuls, their supporters and detractors have already begun sizing one another up, plotting strategy and assessing chances.

As yet, no whisper campaigns or well-timed leaks to the news media have sprung up. But if past papal transitions are any guide, that could just be a matter of time.

“I’m sure we’ll see it,” said John Allen, a veteran Vatican watcher for the National Catholic Reporter.

As spiritual and prayerful as the process is supposed to be, cardinals have been known to resort to more worldly methods of advancing their favored candidates or issues.

“They are talking with one another — not in public view, obviously,” Allen said, and some also have made brief statements to the news media.

One of the issues expected to arise is the internal workings of the Vatican, which has come under heavy scrutiny in the wake of the leaked papal documents. The papers painted an unflattering portrait of an institution racked by turf battles and corruption at the highest levels, and suggested that Benedict was unable to curb abuses.

The pope’s personal butler was arrested and convicted by a Vatican tribunal of stealing the private papers. Benedict later pardoned him and commissioned the three cardinals to investigate.

One recent Italian news report, citing anonymous sources, said the top-secret dossier on the so-called Vatileaks scandal contains revelations of a gay lobby within the Vatican, some of whose members were being blackmailed over their sexuality.

Vatican officials have labeled such reports as baseless and malicious. But that has not stopped some Vatican watchers from wondering whether some mudslinging is already under way, although no one has quite yet divined who benefits and who doesn’t from the speculative accounts of the dossier’s contents.

This week, the Vatican said the confidential report, which Benedict has read, would be handed over only to his successor and not be made available to the rest of the cardinals. But the three prelates who compiled the dossier will attend the general congregation and could divulge some of its findings.