Two bishops in the Roman Catholic Archdiocese of St. Paul and Minneapolis resigned their posts Monday, the second time this spring that American church leaders have stepped aside after complaints over their handling of sexual abuse claims involving priests. In Minnesota, Archbishop John C. Nienstedt and an auxiliary bishop, Lee A. Pich, announced their departures less than two weeks after prosecutors in St. Paul accused the archdiocese of willfully ignoring warning signs of a pedophile priest. Their resignations followed the April exit of Bishop Robert W. Finn from the Diocese of Kansas City-St. Joseph in Missouri, who had been convicted of a misdemeanor for failing to report a priest who took pornographic pictures of girls. Under Pope Francis, the Vatican has stepped up efforts to hold bishops accountable for covering up or failing to take action in sexual abuse cases, including the announcement last week of a tribunal to weigh such cases. John J. Choi, the prosecutor in Ramsey County, Minn., said the resignations would not affect his office's criminal and civil cases against the archdiocese, which accused church leaders of failing to intervene against a priest despite repeated complaints of misconduct. That priest ... has since been defrocked and imprisoned on sexual abuse charges. Since ... 1978, 16 other bishops have resigned or been forced from office under a cloud of accusations that they mishandled abuse cases, according to research by BishopAccountability.org, an advocacy group.