He wears his faith on his sleeve. Well, more specifically, he wears it on his left wrist, tucked under his cuff and just below the band of his wristwatch. It is hard to spot, but it has been there every day since the death of his boy.

“I have not taken off the rosary Beau was wearing when he passed,” Joe Biden told Megyn Kelly two Novembers ago, back when he was settling into a brief recess as a private citizen. The rosary, he explained, “is my connection to him.”

The string of prayer beads remains, and so does his faith as the former vice president now attempts a return to the White House. Biden is the front-runner to take on President Trump. Biden was also the only Catholic on stage at the last Democratic primary debate.

The rosary on the wrist could be another connection, this one to the more than 51 million Americans who share his faith.

Wander a parking lot after Mass in the Midwest, and chances are good a couple of minivans will communicate the same message: “I am Catholic & I VOTE.” It is a bumper sticker, and an indisputable fact of American politics. “Catholic voters are the largest Christian denomination in battleground states like New Hampshire, Wisconsin, and Pennsylvania,” explains John Della Volpe, director of polling at the Harvard Kennedy School’s Institute of Politics (and a partner in RealClear Opinion Research). “Since 1952, they’ve voted for the winner in 13 of 17 presidential elections.” In short, where they go, the popular vote often follows.

Whoever wins over Catholics come 2020 may very well inherit the White House. A RealClearPolitics survey of these voters one year from next November showed that they favor Trump -- but just barely. The philandering, thrice-married president has the soft support of 51% of American Catholics. Another 41% swear they will never vote Trump. An additional 8% say it is unlikely that they would pull the lever for him.

Dig a little deeper into that 51% of Catholic voters inclined to support the incumbent, and a possibility emerges that could torment Trump: 9% report that “it is possible” they would vote for him, not that they will vote for him. Coincidentally enough, Holy Writ associates the number nine with suffering and grief, a likely outcome for the GOP if these voters fall away from the president.

This makes the nominee Democrats pick in the primaries all the more important for the general election.

Faith transcends all things, and not just at this time of the year, pollsters’ spreadsheets included. Those who’ve studied it the most scoff at the idea of a unified “Catholic vote,” including prominent Catholic intellectual George Weigel. Not only does it not exist anymore, he says, it probably hasn’t existed since the years immediately following the presidency of John F. Kennedy, the first and only Catholic to win the White House.

Rome doesn’t dictate the direction of Washington, D.C., of course. Separation of church and state aside, the Vatican cannot even reliably put Catholics in pews for Sunday Mass. “There is voting-by-regularly practicing-Catholics, which skews heavily Republican,” Weigel explains and then there is “voting-by-self-identified-but-not-regularly-practicing-Cathllics, which skews heavily Democratic.”

Whether devoted in their personal faith or not, Catholics seem positively inclined toward Joe Biden. According to the RCP survey, 29% support him while another 24% favor a self-described “democratic socialist,” Vermont Sen. Bernie Sanders.

A reflection of the national electorate, Catholics favor each of the top-tier Democratic challengers in a head-to-head match-up with the president.

Disregard of doctrine is not of concern to Catholic voters in the political aggregate. Pete Buttigieg, the openly gay mayor of South Bend, Ind., leads  Trump  among Catholics. This even though Catholic catechism condemns homosexual activity as “contrary to the natural law.”

And it isn’t just gay marriage. Policy contrary to church teaching is not disqualifying in the aggregate eyes of Catholic voters. According to a comprehensive analysis from the American National Election Studies, Hillary Clinton carried U.S. Catholics in 2016 by a margin of 48% to Trump’s 45%. She has supported abortion throughout her career, sanctioned gay marriage, and endorsed the death penalty in certain situations. The church condemns each, but Clinton still won over Catholics. 

At a moment when the Democrats’ presidential field has shifted left, this willingness to tune out church doctrine in the voting booth could comfort the candidate whose faith does not strictly govern his or her policy positions. Biden’s transgressions include his evolution on abortion and gay marriage, let alone the time he stood by President Obama when the federal government mandated that the Little Sisters of the Poor, an order of celibate nuns, provide health insurance that covers contraception.

It wasn’t a big issue during the last general election, remembers Erick Erickson, a prominent conservative evangelical. But the Little Sisters case did resonate with religious communities. “Make it a national argument,” Erickson argues, “and I think you see a shift in Catholic voters.”

Looking from the outside in, Erickson observes in Biden a candidate who keeps his faith up his sleeve. He won't be heavy-handed during the primary, but if he wins the nomination “he will make sure the rest of America knows that he is a good Catholic who has gone to Mass.” All of it, Erickson suspects, “is part of running as far left as possible to get the nomination and then running back to the center.”

This won’t bother liberal Catholics, the ones George Weigel says identify with but don’t regularly practice their faith -- the ones who turned out for Clinton last time. What will resonate, and what has resonated enough to keep Biden in first place, is a message of renewal. The former vice president talks about the heart of the country, says “we are in a battle for America’s soul.” His emphasis is on what might be best described as civic religion.

The nation has lost his way, in the Biden telling, and he is best suited to bringing about a national sanctification that restores “hope over fear” and “unity over division” and “truth over lies.”

The former senator has spoken at length about his faith, sharing a testimony that would sound scripted if the tragedy described weren’t real, well-documented, and heartbreaking.

It was the winter of 1972 and Biden had just won election to the Senate when a tractor-trailer smashed into the family station wagon. His two sons made it out alive. His wife and infant daughter did not. They were going Christmas shopping.

Biden would say later that he felt “God had played a horrible trick on me.”

It was the spring of 2015 next when Biden’s eldest son succumbed to brain cancer. A veteran and an accomplished lawyer, Beau was destined to be governor of Delaware, party brass believed. Beau died at Walter Reed. He was just 46.

Biden, faced with personal tragedy again, would later remark that “the pain fades a little bit” with time.

These experiences provide a backdrop for a candidate who has overcome much -- so much that, while politicians can’t normally get away with quoting existentialist philosophers, Biden can. “You know, Kierkegaard said faith sees best in the dark,” he said on the Houston debate stage in September, quoting that Danish philosopher and theologian. “And I lost my faith for a while,” he continued, but “I came back.” He also lost his boy, Biden continued, and that “was like losing part of my soul.”

None dare say that Biden does not understand grief, nor question his faith, even if it does not conform with official teaching of the Roman Catholic Church. All the same, a South Carolina priest didn’t care about politics when he recently denied the candidate communion. Biden supports abortion and was, therefore, barred from receiving the sacrament. Denying him the presidential nomination, however, is not something any priest, bishop, or pope can control. That’s up to the voters, Catholic and non-Catholic. And Biden’s faith, imperfect though it may be in the eyes of church leaders, may help him.

Matthew Green teaches politics at Catholic University and expects that voters, even those who don’t practice their faith regularly, may place a premium on religious affiliation, especially in contrast to the current president. After four years of Trump’s smash-mouth politics, Green believes that candidates can gain an advantage by demonstrating empathy and sympathy through their words and deeds.

“And to the extent a candidate can say ‘this is my religion and I draw those traits from my faith,’ that could be very attractive to people, even those who aren’t religious,” Green concludes. 

It is possible that Biden may never compete for the practicing Catholics who approach the ballot box with the catechism in mind. It is realistic, also, to believe that on its own his faith won’t sway primary voters in an increasingly secular party. But come a general election, those 9% of Catholics, the ones who said they were open to but not certain of Trump, could send him to the White House.

This would make Biden the first president to wear a rosary in the Oval Office since John Kennedy.