Since his inauguration two weeks ago as the nation's second Catholic president, Biden's devout Christian faith has become a new flashpoint within a church already reeling from years of moral and financial crises.
"I'm saying to our people, let's use this teaching moment. Let's come together and become more, if you will -- use the questions of faith and respond to them in an intelligent way," said the Rev. Kevin Gillespie, pastor of Holy Trinity Catholic Church in Georgetown where Biden has worshipped twice since becoming president.
"They applauded for a fellow parishioner, a fellow Catholic and the president of the United States," Gillespie said of the welcome Biden received. "People were very happy, not that they all agree with his views, but he's one of us."
While millions of Catholics have celebrated the ascension of one of their own to the White House, some have been publicly questioning whether Biden should be considered a model of their faith.
"You might have heard that the president is Catholic. Perhaps you heard that. Perhaps you heard that he went to mass," said the Rev. Brian Lynch of Transfiguration Catholic Church in Oakdale, Minnesota, in a sermon posted online Jan. 22. "I don't care! That does not impress me!"
The Rev. Jim Gigliotti of St. Andrew Catholic Church in Fort Worth, Texas, told parishioners last month that Biden is a man "without value."
"You don't like it, well that's your problem," he said in a livestreamed homily.
Many Catholic clergy and faithful are passionately fixated on Biden's support for abortion rights, which the church staunchly opposes and considers an issue of "preeminent" importance.
"Some of you I know voted for someone who is now going to suffer and persecute the church for the next four years. That, on top of the fact that he supports the slaughter of the unborn," the Rev. Jeffrey Kirby admonished members of his congregation at Our Lady of Grace Catholic Church in Indian Land, South Carolina, last month. "What have you done? What have you done to your church?"
A majority of Catholics, 52%, backed Biden for president in the 2020 election, according to a national exit poll of voters. Many admire Biden's sincere religious practice, which he has described as a source of solace and purpose.
Gillespie said some of the scrutiny of Biden's faith is "very unfair."
"The anger, the vitriol," he said, "but to question a person's position? That's part of the faith tradition. Using your reason."
On Inauguration Day, the extraordinary rift over Biden among Catholics burst into view.
In a public letter to the new president, Pope Francis expressed "cordial good wishes," urging Biden to embrace "authentic justice and freedom" with respect for "the poor, the vulnerable and those who have no voice."
"Pope Francis has talked about the need to find a better kind of politics, a less polarizing kind of politics. And I think in that sense, he's expressing his hope that Joe Biden could be the one to open that conversation," said Kathleen Sprows Cummings, director of the Cushwa Center for Study of American Catholicism at the University of Notre Dame.
But the church's American leaders took a strikingly different tone.
Archbishop Jose Gomez of Los Angeles, who heads the U.S. Conference of Catholic Bishops, praised Biden's "piety and personal story" in a lengthy statement but warned that the new president "would advance moral evils and threaten human life and dignity, most seriously in the areas of abortion, contraception, marriage and gender."
"There's so much enthusiasm among some in the Catholic world that Trump is no longer president that they are willing to uncritically accept everything from President Biden, and that's a dangerous, dangerous place to be," said Jayd Henricks, former chief lobbyist for the U.S. Catholic bishops.
Some of Biden's early actions on abortion have deepened those concerns. Two days after taking office, he recommitted to "codifying Roe v. Wade." Last week, Biden moved to roll back a ban on U.S. foreign aid to groups that fund abortions or provide referrals, the so-called "Mexico City Policy."
"It's a grave, grave sin," Henricks said of abortion. "And those who are, you know, manifest in commitment to it in a public way persistently are endangering their souls. The church is clear about that."
Gillespie agreed that abortion is a central issue, but questioned the preeminence some Catholic leaders give it.
"It's highly significant, but there is the issue of poverty; of capital punishment; of war. There's other issues that with the Pope saying -- let's not get into a cultural war so that we're divided, let's unite and build bridges," he said.
Biden opposes abortion as a personal matter, but wrote in his 2007 memoir that he doesn't "have a right to impose my view on the rest of society."
As a senator, Biden voted multiple times to uphold a ban on federal funding for abortions but his position has evolved. As president, he said the ban should be lifted.
Biden's position has incensed some Catholic clergy, including a South Carolina priest who in 2019 denied Biden the sacrament of Holy Communion.
"It's the only time it's ever happened and we didn't talk about it. He went to the press and talked about it. It's not a position I've found anywhere else including from the Holy Father, who gives me communion," Biden told the PBS NewsHour in a subsequent interview.
The pope and Washington's new Catholic leader, Cardinal Wilton Gregory, have said they are not going to deny Biden the sacrament. Gregory told Catholic magazine "America" last month that he wants a "conversational relationship" with the president, "even in those areas where we obviously have some differences."
"It may just seem an internal squabble or tussle among Catholics, but it's bigger than that," said Villanova University theology professor Massimo Faggioli, author of "Joe Biden and Catholicism in the United States."
"What happens internally (in the Church) has political and social consequences on the whole country, even if it's not always visible," Faggioli said.
One in five Americans identifies as Roman Catholic, the largest Christian denomination in the U.S., according to Pew Research Center. While the faithful have long been divided in matters of theology and politics, Catholic values aren't exclusively red or blue.
"Right now Catholic Democrats look more like Democrats than they do Catholics. And Catholic Republicans look more Republican than they do Catholic," said Cummings at Notre Dame. "Biden has a chance to help us all to think about how we might talk to each other, to not diminish the defense of the unborn. Really no leader has been in a position to do that."
A civil conversation between Catholic Democrats and Republicans on the issue of abortion and other critical issues of social justice is something many clergy say Biden could help facilitate.
"I am surprised by the vitriol because I think that it's very important now in our country to disagree civilly," said Monsignor Paul Dudziak, pastor of St. Stephen Martyr Catholic Church, a few blocks from the White House where President John F. Kennedy worshipped. "And I'm not sure that a tremendous amount of anger is any help in trying to have a civil society."
"Politics is the art of compromise," said Henricks, the former lobbyist for the U.S. Catholic bishops. "So the church has to acknowledge the fact that -- to advance the common good and fundamental human rights, there will be a need for compromise from time to time."
Gillespie said Biden will always be welcome at Holy Trinity, the oldest Catholic church in the nation's capital.
"It's an opportunity to work towards healing and justice from a faith tradition through this remarkable man," he said.