Kalin, now deceased, reportedly made sexual advances toward seminarians, asked them to help him shower, and would invite seminarians on trips to Las Vegas or for late-night drinks.
Some reports accused Conley's predecessors of failing to take seriously allegations against Kalin, although an August 2018 statement from the diocese said it had "addressed these allegations of misconduct directly with Msgr. Kalin during his time in priestly ministry."
After the Kalin report emerged, Conley ordered reviews of diocesan policies regarding clerical conduct and accountability, made personnel changes in the diocesan curia, and help listening sessions in the diocese about clerical abuse or misconduct.
Several Lincoln priests were subsequently removed from ministry, and Conley apologized for the way he had handled a 2017 report that a priest had "developed an emotionally inappropriate, non-sexual relationship with a 19-year-old male which involved alcohol."
The priest was removed from ministry and sent to a treatment center in Houston before allowing him to return to ministry.
Conley said that he attempted to act with integrity, telling the parishioners that the priest had gone away for health reasons. But while he said he did not cover up the situation or oblige anyone to keep silent about it, he said he regrets failing to act with more transparency.
"Even though we were not legally obligated to report the incident, it would have been the prudent thing to do. Because the young man had reached the age of majority, we did not tell his parents about the incident," Conley said last August.
In September 2018, Nebraska's attorney general initiated an investigation into whether the state's three dioceses had mishandled or covered-up allegations of abuse or misconduct. A report on that investigation has not yet been issued.
The diocesan press release did not cover what role Lucas will play in addressing those matters, though Conley's letter said he had worked with the archbishop "for a smooth transition, with the full support of my senior staff."
Conley, 64, became Lincoln's bishop in November 2012. He had been an auxiliary bishop in the Archdiocese of Denver since 2008 and had worked in the Vatican's Congregation for Bishops from 1996 until 2006.
The bishop's announcement comes days after a report from the Associated Press chronicled the mental health challenges experienced by priests, and noted the propensity of ministry leaders toward depression and other difficulties.
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Conley wrote that he is hopeful about his medical leave of absence.
"Jesus Christ is the Divine Physician, who offers us the grace of healing. I entrust myself to the healing power of Christ, and the intercession of the Blessed Virgin Mary," the bishop wrote.
"I am grateful to be your bishop, and I love the Diocese of Lincoln. It will be difficult to be away. Please pray for me, as I pray for you."