In the summer of 2004, the Vatican sent a letter to the United States addressing one of the hottest issues facing the church here -- whether politicians who back abortion rights should receive Holy Communion. The Congregation for the Doctrine of the Faith sent the guidelines to the leader of the Archdiocese of Washington, D.C. However, Cardinal Theodore McCarrick chose not to share the letter with America's bishops, which kept its blunt contents secret -- until a leak in Italy.

"The Church teaches that abortion or euthanasia is a grave sin," warned the letter, adding that there is a "grave and clear obligation to oppose" civil laws and judicial decisions that "authorize or promote" these acts. At the same time, it explained that there "may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not ... with regard to abortion and euthanasia."

On the central issue, the guidelines said when a person's "formal cooperation becomes manifest (understood, in the case of a Catholic politician, as his consistently campaigning and voting for permissive abortion and euthanasia laws), his Pastor should meet with him, instructing him about the Church's teaching, informing him that he is not to present himself for Holy Communion until he brings to an end the objective situation of sin and warning him that he will otherwise be denied the Eucharist."

Months later, the letter's author -- Cardinal Joseph Ratzinger -- became Pope Benedict XVI. There is no evidence his views have changed.

However, the status of politicians who clash with Rome remains controversial, especially when Catholics occupy strategic positions on the U.S. Supreme Court, in the president's cabinet and on Capital Hill.

Tensions from the Ratzinger letter were also felt during the public events marking the passing of Sen. Edward Kennedy, one of the most symbolic and influential Catholics in American political history.

Catholics on both sides of the aisle dissected the rites, seeking signs of favor or disfavor. The outspoken Cardinal Sean O'Malley of Boston presided in the funeral Mass, but played a small role. Was that important? Where were the region's other bishops? Were television crews told to avoid camera angles that would reveal who received Communion?

But the most symbolic moment occurred during the graveside service in Arlington National Cemetery. That's when the now retired Cardinal McCarrick -- a close friend of Kennedy -- read the dying senator's private appeal for a final papal blessing.

"I know that I have been an imperfect human being, but with the help of my faith, I have tried to right my path," wrote Kennedy. "I want you to know, Your Holiness, that in my nearly 50 years of elective office, I have done my best to champion the rights of the poor and open doors of economic opportunity. I've worked to welcome the immigrant, fight discrimination and expand access to health care and education. I have opposed the death penalty and fought to end war. ...

"I have always tried to be a faithful Catholic, Your Holiness, and though I have fallen short through human failings, I have never failed to believe and respect the fundamental teachings."

McCarrick read excerpts from a Vatican reply, keeping some parts private. The final lines, written by a papal aide, were simple: "Commending you and the members of your family to the loving intercession of the Blessed Virgin Mary, the Holy Father cordially imparts his Apostolic Blessing as a pledge of wisdom, comfort and strength in the Lord."

Kennedy's letter raised a familiar and haunting question: Are the Catholic doctrines on the sanctity of every human life, from conception to natural death, part of the church's "fundamental teachings" or not?

While praising the senator's career, McCarrick added what was almost certainly a gentle reference to his clashes with the church on abortion, gay rights and other doctrinal issues. The bottom line: Kennedy maintained a 100 percent pro-abortion-rights voting record, according to NARAL Pro-Choice America.

"They called him, 'The Lion of the Senate,' and indeed that is what he was," said the former shepherd of the Washington archdiocese. "His roar, and his zeal for what he believed, made a difference in our nation's life. Sometimes, of course, we who were his friends and had affection for him would get mad at him when he roared at what we believed was the wrong side of an issue."