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.