The battle lines are complex, but in Mr. Melloni’s view, the cardinals who want to undermine Cardinal Bertone and, by implication, the pope come from more traditionalist branches of the church. Others see the infighting as more about influence and money — in which powerful conservative Catholic groups like Opus Dei and Communion and Liberation may play a role — than about any larger ideology.

Critics inside and outside the church say that Cardinal Bertone, 77, has been a weak chief executive to a theologian pope with little interest in governing, and some of the documents seem to bear this out. In one, Archbishop Carlo Maria Viganò complained of corruption and cronyism in the awarding of construction contracts and alleged that Cardinal Bertone had been influenced by outsiders in Italian political circles.

Other documents provide a window into power clashes over the Vatican bank’s troubled efforts to meet international transparency standards. In one letter that appeared this year, Cardinal Attilio Nicora, the head of an internal financial watchdog that the Vatican created in 2010, said that the Vatican bank had refused to provide details on suspicious bank activities before an anti-money-laundering law went into effect in 2011.

Mr. Nuzzi’s book also includes letters by Ettore Gotti Tedeschi, the Vatican bank president from 2009 until he was ousted by the board of directors on May 24, a day before Mr. Gabriele’s arrest was announced. Mr. Gotti Tedeschi, whom some Italian media reports have described as a member of Opus Dei, has said in interviews that some in the Vatican were blocking his efforts to make the bank more transparent.

Who exactly is behind the leaks is the subject of perhaps the most intense speculation. In Corriere della Sera, a well-respected judicial reporter, Fiorenza Sarzanini, wrote that Mr. Gabriele’s appointment to the papal household in 2006 had been sponsored by Cardinal Leonardo Sandri, the prefect of the Vatican’s Congregation for Eastern Churches and an Argentine with a power base inside the Vatican hierarchy. She noted that Mr. Gabriele was a member of Communion and Liberation, hinting that its interests may also be in play.

In a front-page editorial in La Repubblica on Friday, the editor in chief, Ezio Mauro, said the leaks were part of an orchestrated campaign by unnamed forces within the Vatican aimed at undermining Cardinal Bertone, so that they could have more influence in a future conclave to elect a new pope. “It is an operation both primitive and extremely modern in its elementary violence, made of ink and paper in the Internet era,” Mr. Mauro wrote.

The scandal has caused the Vatican to shift once again into crisis-management mode. The Vatican spokesman, the Rev. Federico Lombardi, held daily news briefings last week to deny press reports, including Ms. Sarzanini’s as well as several that reported a meeting between Cardinal Bertone and an Italian industrialist to discuss the Vatican’s buying an Italian bank so that it could meet international transparency norms without changing the secretive Vatican bank.