Sexual abuse by Catholic priests and its cover up by bishops was always going to dominate this past weekend’s trip by Pope Francis to Ireland, but the explosive culmination of the trip with calls for his resignation was a surprise. Late Saturday night, an 11-page letter attributed to former Vactican diplomat Archbishop Carlo Maria Viganò was published by a number of conservative Catholic sites in the United States and Italy. In it, Viganò alleged that Francis not only knew about charges of sexual misconduct committed by former Washington Cardinal Theodore McCarrick, but that Francis actually helped to rehabilitate the cardinal after Pope Benedict XVI removed him from public life.

The pope’s critics immediately called for his resignation. His supporters remain skeptical, suspecting that the forces that have plagued Francis since the start of his papacy are again trying to undermine his reform. Sorting through the allegations is difficult: As of yet, there is no clear corroborating evidence.

Viganò, who served as the Holy See’s representative to the United States from 2011 until 2016, alleges that the Vatican learned as early as 2000 of rumors of sexual misconduct involving McCarrick and young seminarians. McCarrick is alleged to have sexually harassed and assaulted seminarians during his time as a bishop in New Jersey in the 1980s and ‘90s by inviting seminarians to a beach house he owned, forcing them to share his bed, and pressuring them into sexual situations.

But Viganò uses vague language and euphemisms to describe what McCarrick did, so it is unclear if he told the Vatican or Pope Francis that he believed the former cardinal was guilty of abuse.

The Vatican, and specifically the retired pope’s staff, ignored warnings about McCarrick’s predatory behavior numerous times during the papacy of Benedict XVI, Viganò says: Memos he says he sent in 2006 and 2008 were not answered. Eventually, the former diplomat alleges, his warnings were taken seriously and Pope Benedict XVI imposed sanctions on McCarrick, in either 2009 or 2010, which he says forced McCarrick to move from a seminary where he was living in Washington and end his public ministry. Viganò also claims that McCarrick’s successor in Washington, Cardinal Donald Wuerl, was informed of the sanctions, though Wuerl denies being given information about them.

Shortly after Pope Francis was elected in 2013, Viganò says, the new pontiff lifted the alleged sanctions, eager to rehabilitate a cardinal whose more liberal stance aligned with the new pope’s.

Absent from Viganò’s letter is the allegation that eventually prompted Pope Francis to remove McCarrick from ministry: In June, the Archdiocese of New York announced that an allegation that McCarrick had sexually abused a minor more than 45 years ago had been substantiated. In July, McCarrick resigned from the College of Cardinals.

Viganò does not say in the letter that he explicitly told Francis that McCarrick sexually assaulted seminarians; the letter says Francis asked Viganò his thoughts on McCarrick, and that Viganò told the pope that McCarrick “corrupted generations of seminarians and priests.” The pope, Viganò says, did not reply.

The letter goes on to say that anyone who had knowledge of McCarrick’s sexual misconduct and who did not act—a group he says includes Pope Francis and Wuerl—should resign.

The letter cannot be dismissed easily. After all, this is a former high-ranking church official calling on the pope to resign. During his time in Washington, Viganò would have had access to the inner workings of the U.S. church, and he is making very specific allegations that can be corroborated or, in some instances, found to be untrue.

Pope Francis’s record on sex abuse has previously been called into question, making Viganò’s accusations at least plausible. Francis was slow to acknowledge sexual abuse by clergy in Chile; he has been defensive about the church’s current practices in combating sexual abuse; and just this weekend, he described a prominent victim-advocate, who has been supportive of the pope’s efforts at reform, as being “fixated” on the need for the church to hold bishops accountable.    

But there are also good reasons to treat Viganò’s claims with skepticism. For one, a central claim of the letter—that Pope Benedict removed McCarrick from public ministry—is being questioned. In 2011, a year or two after Benedict allegedly imposed sanctions, McCarrick preached at Saint Patrick’s Cathedral, ordained priests in New York, testified before the U.S. Congress and appeared on Meet the Press. The next year, McCarrick visited the Vatican with other U.S. bishops, where he attended a birthday party for Pope Benedict. Viganò stood near McCarrick at an awards dinner in New York in May 2012 and in 2013, McCarrick was seen shaking the hands of Benedict before the pope abdicated. McCarrick later celebrated Mass in Washington alongside Viganò.

Then there are questions about Viganò’s motives. The former nuncio opposes the Francis papacy’s reforms, and he has joined a group that routinely challenges the pope’s welcoming of divorced and civilly remarried Catholics to Communion and his (relatively) more progressive views on homosexuality.

In fact, much of Viganò’s letter is devoted to condemning homosexuality. For example, he claims a “homosexual current in favor of subverting Catholic doctrine on homosexuality” is to blame in the church’s current crisis.

Most of the men Viganò names in his letter also happen to be his ideological opponents. Not least among them is Pope Francis himself, who in 2016 recalled Viganò to Rome, in part because he was unhappy with the nuncio’s role in arranging a 2015 meeting in Washington between Francis and Kim Davis, the former Kentucky clerk who refused to sign a marriage certificate for a same-sex couple.

Viganò also claims that McCarrick was instrumental in the selection of three influential U.S. bishops who are seen as allies of Francis, a charge that could undermine their ministries. Each of them—Cardinal Blase Cupich of Chicago, Cardinal Joseph Tobin of Newark and Bishop Robert McElroy of San Diego—released statements dismissing the letter and calling out factual inaccuracies.   

When it comes to sexual abuse, Viganò’s own record is checkered, which may undermine his claims that his conscience demanded he make these allegations against McCarrick public. In 2014, Viganò is reported to have prematurely ended an investigation into allegations that Archbishop John Nienstedt, a conservative and an outspoken critic of same-sex marriage, mishandled sex abuse allegations. During that investigation, allegations of sexual misconduct by Nienstedt himself surfaced, and there are claims that Viganò ordered that an incriminating letter be destroyed. Nonetheless, Nienstedt stepped down from his post in 2015.

The timing of the letter’s release also raised eyebrows, as it hit the Internet just hours before Pope Francis would fly from Ireland back to Rome. This meant Pope Francis would face the press during his customary in-flight press conference and that the letter’s charges would dominate the news cycle, rather than the trip itself—a striking parallel to the pope’s 2015 visit to the U.S., where news of the pope’s meeting with Davis was released just as the trip wrapped up.

When asked about the allegations during Sunday’s press conference, Francis said he would not comment. He urged journalists to look into the claims and to come to their own conclusions. But he did not rule out commenting in the future.

The allegations raised by the archbishop come at a time when confidence in Francis’ papacy appears shaky. Sexual abuse in the church is once again dominating the headlines, and the Vatican seems unable to quell criticism that it understands the gravity of the situation. But when it comes to victims themselves, some are accusing Viganò of co-opting their trauma to advance his own agenda.

As Juan Carlos Cruz, a survivor of sexual abuse by a priest in Chile, put it in a tweet on Monday, Pope Francis has work to do when it comes to holding priests and bishops accountable.

But, he asks, “where was Viganò when it came to do something for victims? He is just a fanatic who blames gays and represents ultra conservatives who want power and use survivors as their way to get it.”