In the summer of 2016, two White House staffers -- Brian Mosteller and Joe Mahshie -- tied the knot in a rite led by one of America's most prominent Catholics.

The officiant was Vice President Joe Biden, who later proclaimed on Twitter: "Proud to marry Brian and Joe at my house. Couldn't be happier … two great guys."

Leaders of familiar Catholic armies then debated whether Biden's actions attacked this Catholic Catechism teaching: "The marriage covenant, by which a man and a woman form with each other an intimate communion of life and love, has been founded and endowed with its own special laws by the Creator. … Christ the Lord raised marriage between the baptized to the dignity of a sacrament."

Conflicts between bishops, clergy and laity will loom in the background as Biden seeks to become America's second Catholic president. Combatants will be returning to territory explored in a famous 1984 address by the late Gov. Mario Cuomo of New York, entitled "Religious Belief and Public Morality."

Speaking at the University of Notre Dame, he said: "As a Catholic, I have accepted certain answers as the right ones for myself and my family, and because I have, they have influenced me in special ways, as Matilda's husband, as a father of five children, as a son who stood next to his own father's death bed trying to decide if the tubes and needles no longer served a purpose.

"As a governor, however, I am involved in defining policies that determine other people's rights in these same areas of life and death. Abortion is one of these issues, and while it is one issue among many, it is one of the most controversial and affects me in a special way as a Catholic public official."

It would be wrong to make abortion policies the "exclusive litmus test of Catholic loyalty," he said. After all, the "Catholic church has come of age in America" and it's time for bishops to recognize that Catholic politicians have to be realistic negotiators in a pluralistic land.

Cuomo also noted polls indicating that American Catholics "support the right to abortion in equal proportion to the rest of the population. … We Catholics apparently believe -- and perhaps act -- little differently from those who don't share our commitment. Are we asking government to make criminal what we believe to be sinful because we ourselves can't stop committing the sin?"

Decades later, New York Gov. Andrew Cuomo offered a blunt take on his father's logic while defending the 2019 Reproductive Health Act, legislation the New York State Catholic Conference called "tragic" and "horrendous."

"As a Roman Catholic, I am intimately familiar with the strongly held views of the church," he wrote in The New York Times. "Still, I do not believe that religious values should drive political positions. … Only by separating constitutional duties from religious beliefs can we have a country that allows all people the ability to pursue their own theological and moral principles."

The problem with these important Catholic debates is that the crucial issue isn't whether Catholic politicians can be active participants in efforts to negotiate centrist policies on controversial issues, said philosopher Francis Beckwith, who also teaches Church-State Studies at Baylor University.

At Notre Dame, Mario Cuomo correctly noted that Catholic politicians have to "take into consideration what citizens believe and how they act. However, it's something else when Catholics choose to act on these matters and work to support political movements and legislation that completely undercut church teachings," said Beckwith, who made news in 2007 when he returned to Catholicism, while serving as president of the Evangelical Theological Society.

Debates about Biden's Catholic identity and practice, he added, will almost certainly focus on his actions -- more than his words.

"If you read the Notre Dame speech closely, Cuomo is saying he believes church teachings are true, but that, in public life, we need to cooperate with people who have other beliefs. I don't think that's what Biden is saying. When he performed a same-sex marriage, he was saying -- with his actions -- that this rite was good and that the church's teachings are wrong. At that point, it would appear that Catholics are perfectly free to oppose whatever church teachings they reject."