When John F Kennedy was running for US president in 1960, he addressed a group of protestant ministers in Houston, Texas, many of whom questioned whether, as a Roman Catholic, he could act independently of the Vatican.
“I am not the Catholic candidate for president. I am the Democratic party’s candidate for president, who happens also to be a Catholic,” said Kennedy, who went on to win the election.
Kennedy was the first and only Catholic US president. Six decades later, Joe Biden, another Democrat, is hoping to become the second.
But this time around, the Biden team sees the candidate’s faith as an asset, rather than a liability. The former vice-president has made concerted appeals to Catholics, an increasingly racially and ideologically diverse group who make up around a quarter of the voting population and are seen as reflective of the wider electorate.
“The overall Catholic vote and the national popular vote have tracked very very, closely with each other, election after election,” said Mark Rozell, a professor at George Mason University and a co-editor of a book about Catholic voters.
White Catholics are especially concentrated in key Midwestern swing states such as Michigan, Pennsylvania and Wisconsin — all places Donald Trump won narrowly in 2016.
The growth in the Hispanic population means Catholics are also increasingly well-represented in other parts of the country. In Arizona, another battleground in the south-west, more than one in four adults is Catholic, according to the Public Religion Research Institute.
Mr Biden, who attends church weekly and often carries rosary beads, frequently invokes his faith on the campaign trail, telling stories about the nuns who taught him as a child in school, or talking about how religion helped him cope with the loss of his first wife and two children.
In a speech last month in Pittsburgh, Pennsylvania, he quoted Pope John Paul II; campaign ads include images of the former vice-president with the current pope, Francis, who has been lauded by progressives for his criticisms of unbridled capitalism and calls for action on climate change.
At the same time, the Trump campaign has made its own overtures to more conservative Catholic voters. Timothy Dolan, the archbishop of New York, spoke at the Republican National Convention, and the president appointed Amy Coney Barrett, a devout Catholic mother of seven, to the Supreme Court.
In the countdown to the 2020 election, stay on top of the big campaign issues with our newsletter on US power and politics with columnists Rana Foroohar and Edward Luce. Sign up here
Mr Trump, who identifies as Presbyterian but does not regularly attend church, has made restricting abortion central to his message. Mr Biden last year dropped his longstanding support for the Hyde Amendment, which restricts federal funding for abortions.
Four years ago, Mr Trump won Catholic voters nationwide by a seven-point margin over Hillary Clinton, driven by the overwhelming backing of white Catholics in particular.
But the polling picture has changed. A Pew survey out last week showed Mr Trump still had an edge over his Democratic challenger among white Catholics, but his lead had contracted by 11 points over the summer. The latest poll showed Mr Trump leading Mr Biden, 52-44 with white Catholics. Among Hispanic Catholics, Mr Biden was ahead by nearly 40 points.
Political experts say Mr Biden’s personal faith does not solely explain the shift, which is likely owing, in part, to the president’s broader polling declines among older voters, college-educated women, and other groups that disapprove of his bombastic rhetoric and handling of the coronavirus pandemic.
A separate poll out on Monday from the Public Religion Research Institute showed just 39 per cent of white Catholics and 28 per cent of Hispanic Catholics said the country was “moving in the right direction”.
“Partisan identity has really swamped religious identity when it comes to selecting a president,” said PRRI founder Robert Jones, who added that pundits often overestimate the importance of specific social issues when it comes to the Catholic electorate.
For example, while the official Church teaching opposes abortion or same-sex marriage, polls suggest most voters who identify as Catholic disagree. Even those who do agree with church teachings will often base their electoral choice on other issues.
“[Catholic voters’] priorities and issue positions are often misunderstood because they don’t actually align that well with the official church hierarchy position,” he added. “They just don’t fall on the culture war lines that you would expect.”
Tricia Bruce, a sociologist at the University of Notre Dame, said: “People presume Catholic voters to hold to the teachings of their faith. There is so much survey and interview data that shows to the contrary.”
“It would be inaccurate to predict and assume that Catholics vote one way or another based on an abortion stance,” she added.
Moriah Bauman is a 27-year-old Catholic graduate student from Somerville, Massachusetts, who volunteers for the Biden campaign and rejects Mr Trump’s description of himself as the “most pro-life president ever”, pointing to his support for the death penalty and crackdowns on immigration at the US-Mexico border.
“Being pro-life as a Catholic means working to uphold the sanctity and dignity of life in all stages and in all forms,” she said. “For me, that extends way beyond the issue of just abortion . . . I think about the life of the prisoner on death row and the life of the immigrant who is trying to escape unspeakable violence in their home country.
“As Christians, we are called to live by the commandment: love one another as I have loved you,” she added. “I think it has been very clear since the beginning . . . that President Trump doesn’t love anyone more than he loves himself.”