Joe Biden often crosses himself and looks toward the sky when saying something he jokingly might need to apologize for, regularly referring to the nuns who taught him during 12 years in Catholic school.

Now, several recent TV ads from Biden’s campaign show him standing with Pope Francis or huddled with a Jesuit priest. He’s reading from a pulpit, bowing his head in prayer, or standing solemnly in front of a church’s stained-glass window. And a radio spot includes a parishioner from Biden’s home church talking about how the Democratic presidential nominee is a regular at Sunday Mass.

“That’s Joe Biden, a man guided by faith,” she says.

In the final stretch of a campaign in which Catholic voters are seen by both parties as a decisive bloc in several battleground states, Biden’s campaign has increasingly highlighted his direct connection to the faith — and his potential to make history as the country’s second Catholic president, 60 years after John F. Kennedy became the first.

The strategy comes as President Trump and his allies have sought to portray Democrats as anti-Catholic, seizing on past criticism from some Democratic senators of the conservative Catholic teachings embraced by Supreme Court nominee Amy Coney Barrett.

But the focus on Biden’s Catholicism represents a renewed emphasis in identity politics for Democrats, who have directed much of their attention to the role of Black voters but have not always given prominence to the cultural roots of the White former vice president.

That focus was apparent during the recent vice-presidential debate, when Sen. Kamala D. Harris (D-Calif.), hailed for her history-making role as the first woman of Black or Asian ancestry on a major party ticket, noted: “Joe, if elected, will be only the second practicing Catholic” to become president.

Biden’s advisers see his faith and cultural touchstones — he famously carries a rosary in his pocket and in his youth had aspired to become a priest — as important ways to connect with what they refer to as the “White working-class Catholic vote” in the industrial Midwestern states. They also hope this will help him among Hispanic Catholics in the Sun Belt.

“We’re looking to organize both the Catholics in the pews every Sunday but also the cultural Catholics who were brought up around the church or still align with its social-justice teachings,” said John McCarthy, the Biden campaign’s deputy national political director. “The vice president being who he is allows him to connect. . . . Our best tool for Catholic outreach is Joe Biden.”

Trump, a man of little public faith who has assiduously courted evangelical voters, has tried to undercut the political reach of Biden’s beliefs, accusing him of wanting to “hurt the Bible, hurt God.” A top surrogate — former Notre Dame football coach Lou Holtz — publicly questioned Biden’s standing in the church, calling him “a Catholic in name only.”

He and other Republicans have also defined criticisms of Supreme Court nominee Barrett by any Democrat — including Biden — as unacceptable attacks on her Catholic faith. Trump has cast himself as a prime defender of Catholicism, even as he denigrates his Catholic opponent.

“On the religious situation with Amy, I thought we settled this 60 years ago with the election of John F. Kennedy,” Trump said when he nominated Barrett, exaggerating the Democratic response to her so far, which has mostly centered on whether she would vote against the Affordable Care Act. “But seriously, they’re going after her Catholicism. I will stand with her, fight with her, and we will make sure that these attacks stop.”

Biden on Monday said Barrett’s religious background should be off-limits in any questioning during confirmation hearings. “No, I don’t think there should be any questions about her faith,” he told reporters before traveling to Toledo, an area with 124 parishes.

Biden’s move to accent his Catholic background seeks to avoid defining his faith solely through the lens of abortion rights, which he supports, and will test whether Catholic voters share his perspective. For Biden, abortion rights have already proved to be a central and divisive topic, as it has with other high-ranking Catholic politicians; however, a 2019 Pew Research Center survey found that 56 percent of Catholics support the right to abortion in all or most cases.

Democrats have long claimed that he was not supportive enough of abortion rights — he came out in support of federal funding for abortions only last year — and Republicans have criticized him for deviating from the church’s opposition to abortion. Some U.S. bishops have denied Biden Communion because of his stance, and Catholic schools have not allowed him to speak.

When Biden was selected in 2016 to receive one of highest honors that Notre Dame can confer on an American Catholic, it triggered an uproar among some on the campus who were angry about his stance on abortion rights.

A group of faculty members, the University Faculty for Life, called it “a scandalous violation of the University’s moral responsibility.” By a unanimous vote, the group called on the university to rescind the honor to Biden; the university resisted and conferred the award.

Barrett was a member of the group, but a White House official and three other faculty members in the group at the time told The Washington Post that she had no role in drafting the resolution and was not present when the vote was taken.

Biden, the country’s first Catholic vice president, has rarely mentioned Barrett by name and hasn’t brought up their shared Catholic faith. Biden’s campaign has spread the word among its surrogates to avoid any mention of Barrett’s religious views, sticking to discussions of how she might rule.

“We’re not the campaign that attacks people’s faith. We talk about our values,” said Josh Dickson, a former Republican who is Biden’s faith outreach director. “Around Amy Coney Barrett, it’s fair to look at her record. But our focus is on Donald Trump. Donald Trump is on the ballot, and how he has acted and failed to lead are important to people of faith.”

Catholics make up about one-fifth of the population but are concentrated in key electoral pockets. The industrial Midwest is filled with older Catholics, many of whom grew up in the traditional blue-collar families that helped deliver states such as Pennsylvania, Michigan and Wisconsin to Trump in 2016. Hispanic Catholics — a growing demographic, both in the church and in politics — are concentrated in important Sun Belt states such as Arizona and Florida.

Only 14 percent of Catholic voters said it was important to have a president who shared their religious beliefs, but 62 percent of Catholics said it was very important to have a president who lives a moral and ethical life, according to a February survey by the Pew Research Center.

Catholics who are registered to vote are almost evenly divided between the Republican Party and the Democratic Party, according to Pew Research Center polls. While Hispanic Catholics overwhelmingly lean toward Democrats, the past decade has seen a steady erosion of the number of White Catholics who support the party.

In 2008, when Biden was Barack Obama’s running mate, the Democratic ticket won Catholics, 54 percent to 45 percent, according to exit polls. But in the 2012 reelection campaign, Catholics were evenly split.

The transformation continued in 2016, when 52 percent of Catholics supported Trump, compared with 45 percent for Hillary Clinton, according to a Pew Research Center survey.

“There has been a growing realization that the Catholic vote in 2016 was an influencer in the outcome of that election,” said Mark J. Rozell, who co-edited the book “Catholics and US Politics After the 2016 Elections: Understanding the ‘Swing Vote.’ ” “And one of the keys in this election is the ability of Joe Biden to undercut some of Trump’s support among White Catholics.”

The Trump campaign launched a Catholics for Trump group in April and has coordinators in key states such as Pennsylvania and Wisconsin. His campaign has pointed to Biden’s support for abortion rights as a reason for practicing Catholics to be wary of him. Trump’s campaign has run digital ads touting support from Catholics, and an outside group, CatholicVote, last month launched a nearly $10 million advertising campaign opposing Biden.

“Over nearly 50 years in office, Joe Biden has enacted policies that drastically undermine Americans’ ability to live out their faith in their everyday lives,” said Samantha Zager, a spokeswoman for the Trump campaign.

“President Trump is the most pro-life president in history, a staunch defender of religious liberties, and has a strong track record of appointing conservative judges to the federal bench,” she said. “Biden won’t even announce his Supreme Court list because he knows it would alienate Americans of faith, and his last-ditch attempts to win over religious voters are disingenuous and transparently political.”

Trump’s attraction to Catholics and other religious voters can seem quizzical on the surface. He rarely goes to church and has said he can’t ever remember asking God for forgiveness. He has downplayed the importance of Communion, flippantly saying during his 2016 campaign: “I drink the little wine, which is about the only wine I drink, and I eat the little cracker.”

But he has also reveled in the embrace of evangelicals in what has been a largely transactional relationship. Many have brushed aside his behavior as they confer approval for his policies, especially the judicial appointments that have made the federal bench more conservative.

Trump’s focus on abortion as defining how to appeal to Catholics chooses one aspect of church teaching that conforms to his current worldview — even as many of his other policies are in direct opposition to church positions. Among them: his support for capital punishment, which Biden opposes, and his treatment of immigrants. (Trump in the past had described himself as favoring abortion rights, changing his position a few years before running for president.)

“Being Catholic, trying to align yourself with the Catholic Church when it comes to politics — it’s complicated,” said Rep. Tim Ryan (D-Ohio), who went through 13 years of Catholic schooling. “You have a lot of Catholics who are pro-life saying we’re going to burn in hell because we’re pro-choice.”

“But the Church has a clear position on immigration reform,” he added. “You don’t hear a lot of Democrats telling Republicans they’re going to hell for not being for immigration reform or not doing more social programs for the poor.”

Just as Biden’s reputation as a moderate dealmaker has complicated Trump’s attempts to cast him as a radical socialist, the former vice president’s lifelong faith has made it hard to portray him as a secular adversary.

Biden allies have grown angry over Trump’s suggestions that Biden is “an enemy of God,” to the point that New Jersey Gov. Phil Murphy (D) recently revealed a story that he said reflected Biden’s deep reverence.

On a trip to Germany in 2013 that came at the prodding of Murphy, then the U.S. ambassador to the country, Biden said he had only one favor to ask: Could the ambassador find an English-speaking priest to say Mass for Biden and his family? Murphy located a priest, and about 10 people gathered in a hotel room for the service.

“For the Catholics like me, the notion you’d be traveling on a regular Sunday and go to those lengths, it’s a measure of a guy’s true faith,” Murphy said. “It’s a quiet faith. It’s a genuine faith. He’s not wearing it on his sleeve. Which makes it, in my opinion, even more impressive.”

Murphy said he had kept the moment private until recently, when he grew tired of what he views as unfair attacks on Biden by defenders of Barrett.

“Just as her faith shouldn’t be dragged into it, his shouldn’t either,” he said. “You can’t have it both ways. That’s what these guys do. It’s hypocritical to treat one person and their faith one way and another person and their faith another.”

Catholics for Biden, part of the campaign’s outreach, lists a number of church priorities on its website, including dignity for workers, access to health care and a “humane” immigration policy. The group has been hosting virtual events and phone banking, calling other Catholics to spread Biden’s story and emphasize their shared faith.

“The more we make this personal and real, the more we can talk about who Joe is, how he lives his faith, the more folks get to know him,” said Felice Gorordo, national co-chair of Catholics for Biden.

Seung Min Kim contributed to this report.