For some people, it's such a sensitive topic they would prefer no one discussed it at all. But if Samuel Alito is confirmed to the Supreme Court, it will be the first time in American history that five sitting justices will be Catholic: Alito, John Roberts, Clarence Thomas, Antonin Scalia and Anthony Kennedy.
Approximately 25 percent of the U.S. population is estimated to be Catholic, so a minority religion would be the majority on the court.
It tends not to be something people make an issue out of, at least publicly, but some liberals do have concerns about such a Catholic court.
"There is some fear that they might perhaps, on some issues like abortion, carry out a kind of Catholic jurisprudence rather than reflecting a broader point of view," said John Green, a senior fellow at the Pew Forum on Religion and Public Life.
But for others, Alito's confirmation represents a milestone for a once-oppressed religious minority.
It wasn't so long ago, as Sen. Pat Leahy, ranking Democrat on the Senate Judiciary Committee, brought up during the Alito hearings: "The signs then were 'no Irish need apply' or 'no Catholics need apply.'"
A good deal of anti-Catholicism, Green says, was a staple of American politics.
"Some of this had to do with how the United States was settled," he said. "Some of the original settlers were Protestants who fled Europe because of the then-problems with the Catholic Church. And among many of those Protestants, there was this fear that the Roman Catholic Church through the Vatican would dictate the behavior of American politicians -- so that senators and governors and perhaps even a Catholic president, would answer to the pope and be a Catholic first rather than an American first."
History of Catholic Backlash in Politics
In 1928, Al Smith -- the first major-party Catholic presidential candidate -- was the subject of withering anti-Catholic propaganda.
He even saw a fellow Democrat denounce his candidacy on the Senate floor, warning Americans that Smith's candidacy would mean the Roman Catholic Church "will lay the heavy hand of a Catholic state upon you and crush the life out of Protestantism in America."
In 1960, John F. Kennedy traveled to Texas to defend himself to a group of Houston ministers. That was after his candidacy was condemned by the Southern Baptist Convention, which unanimously passed a resolution voicing doubts that any Catholic should be president.
"I am not the Catholic candidate for president," Kennedy said. "I am the Democratic Party's candidate for president, who happens also to be Catholic. I do not speak for my church on public matters -- and the church does not speak for me."
"I remember that campaign," said Richard Land, president of the Southern Baptist Convention's Ethics & Religious Liberty Commission. "I was 14 years old, and I lived in Houston, Texas, and my pastor came back to our Baptist church and from the pulpit, he said: 'I have good news! President Kennedy told us that on public-policy issues, his church doesn't speak for him and he doesn't speak for his church. And that he's going to separate his Catholicism from his service if he's elected.' And people applauded all across the auditorium. They just thought it was a great thing."
Silence Notable to Some Catholics
That was 45 years ago. Today's silence on the issue is notable even to some Catholics.
"You would think that even at least outside Catholic circles, there would still be more consternation that this might be of some significance that now the pope will be the fifth vote on the court," said Dennis Coyle, a professor at Catholic University of America in Washington, D.C. "It is a sign of how far we've come, I guess, that it is so unremarkable."
It's also a sign of one of the more interesting political shifts in the last few decades -- that of conservative Catholics, traditionally loyal Democrats, joining the Republican Party and its evangelical base.
Issues such as abortion and so-called "values" debates have largely brought these historically warring tribes together to support, for instance, like-minded judicial nominees.
"I have a lot more in common in my worldview with [Pope] John Paul II or [conservative commentator] Bill Bennett, both Roman Catholics, than I do with Jimmy Carter or Bill Clinton or Al Gore, who are all Southern Baptists," Land said.
John Kerry saw the brunt of that alliance when in 2004, as the first Catholic presidential candidate since Kennedy, he lost the Catholic vote.
"John Kerry's Catholicism was not an issue at all for a lot of Protestants," Land said, "but it was a big issue for a lot of Catholics. A lot of my Roman Catholic friends said to me they didn't think Kerry was Catholic enough."
Many Catholic bishops agreed, and the Vatican -- weighing in just before Election Day -- ordered that politicians who support abortion rights should be denied communion.
So would the same pressure be applied to a judge or a justice? Is it fair to even ask?
For instance, the Catholic Church opposes the practice of capital punishment. Do observant Catholic judges not have an obligation to rule that way?
"The answer is no," said legal scholar Douglas Kmiec of Pepperdine University's School of Law. "The judge has no moral responsibility for the laws that his community enacts."
Scholars say, according to the Catholic Church, what is expected of a judge or a justice is not to make laws, but simply to interpret as fairly as possible how the laws made by legislators jibe with the Constitution.
"So judges are responsible for abiding by the morality in their own lives, but they are not responsible for imposing that morality in judicial decision-making," Kmiec added.
For the senators responsible for confirming them, their obligation includes not voting for nominees in any way because of their faith. It's right there in Article VI of the Constitution -- "no religious Test shall ever be required as a Qualification to any Office or public Trust under the United States."
They sometimes get very close, though, as Chief Justice John Roberts found out in his confirmation hearing.
"My faith and my religious beliefs do not play a role in judging," Roberts said. "When it comes to judging, I look to the law books and always have. I don't look to the Bible or any other religious source."
So, ultimately does a majority Catholic court matter? Maybe what matters most of all is that such things don't seem to matter much anymore.