By JASON HOROWITZ
DES MOINES — At a Vatican meeting a few years ago, Pope Benedict XVI unexpectedly asked Vice President Joseph R. Biden Jr. for some advice. “You are being entirely too hard on the American nuns,” Mr. Biden offered. “Lighten up.”
Last year, Mr. Biden seized on an audience with Pope Francis as another opportunity to praise the sisters who remained the target of a Vatican crackdown for their activism on issues like poverty and health care.
And on a visit to Iowa on Wednesday, Mr. Biden literally, as he might put it, got on board with the nuns.
“You’re looking at a kid who had 12 years of Catholic education,” Mr. Biden, wearing a white shirt and a red tie, said before a backdrop of the gold-domed Iowa statehouse and a “Nuns on the Bus” coach bus. “I woke up probably every morning saying: ‘Yes, Sister; no, Sister; yes, Sister; no, Sister.’ I just made it clear, I’m still obedient.”
The issue of obedience has weighed on those nuns of late, as the Vatican has deemed the women on stage with the vice president radical feminists who pay too much attention to social justice and too little to promoting church teaching on issues like abortion and same-sex marriage.
Mr. Biden’s visit came just weeks after Cardinal Gerhard Müller, the Vatican’s enforcer of doctrine, shocked many American nuns with his comments to a Vatican newspaper. As he defended the effort to rein in the nuns, the cardinal remarked, “Above all, we have to clarify that we are not misogynists; we don’t want to gobble up a woman a day!”
So while political reporters focused on Mr. Biden’s appearance as his first foray back into a presidential campaign season, the outing also put the nation’s first Roman Catholic vice president in the middle of a protracted political fight between the pope he admires and the American nuns he reveres.
“All politics begin here in Iowa,” said Sister Simone Campbell, the head of Network, the group that organized the tour and described Mr. Biden’s papal conversations. She expressed delight that the vice president had lent some star power to what she called “our little, teeny event.”
In an interview, Sister Campbell said Mr. Biden had expressed a willingness to join the nuns after their first tour in 2012, “Nuns on the Bus: Nuns Drive for Faith, Family and Fairness.” That was the year that the Vatican’s Congregation for the Doctrine of the Faith cracked down on the Leadership Conference of Women Religious, an umbrella group that represents about 80 percent of America’s 57,000 nuns. The report explicitly cited Sister Campbell’s group, which helped lobby for President Obama’s health care law, as being a particularly bad influence.
The continuing inquiry has prompted tension in the Vatican.
Many Catholic progressives have looked to Francis, who has stripped some of the American church’s most powerful traditionalists of their power in Rome, to end the investigation and affirm that the nuns’ work with the poor is in sync with his own priorities. So far, they have been disappointed.
Sister Campbell said Obama administration officials had offered to help make her group’s case through diplomatic channels and added that the president’s chief of staff, Denis McDonough, a Catholic whosebrother is a priest, “is like totally into” the nuns’ approach to the faith.
Mr. Obama himself has long ties to Catholic activism; he began community organizing under the guidance of progressive priests in Chicago.
But it is Mr. Biden who feels closest to the nuns.
At the event on Wednesday, Mr. Biden said, “The Nuns on the Bus fought like the devil for health care.” He then helped kick off their 10-state tour to increase voter turnout by saying, “I know no group of people who bring a greater sense of justice and passion to what they do.”
The prelates of the church, he suggested, would be wise to listen to the nuns, because “guess what, they are more popular than everybody else.”
The Holy See’s press office declined a request for comment. Privately, Vatican officials’ responses to Mr. Biden’s appearance ranged from indifference to annoyance.
“There will be people unhappy in the Vatican if this becomes an occasion for the nuns to get a big vote of support from the White House,” said Kenneth Briggs, the author of “Double Crossed: Uncovering the Catholic Church’s Betrayal of American Nuns.”
After praising the nuns in hushed tones, Mr. Biden abruptly switched to a shouting campaign mode on the bright afternoon, calling for respect for immigrants, protection of voting rights and restoring the middle class before a crowd of about 250 people.
“What happened? Things are out of whack!” he yelled to applause. (He also quoted Thomas Pynchon and, hours after apologizing for his use of the word “Shylocks” to portray craven bankers, described a Chinese leader as hailing from “the Orient.”) Even more so than former Secretary of State Hillary Rodham Clinton, who was the star attraction at Senator Tom Harkin’s steak fry on Sunday, Mr. Biden was saddled with the weight of defending the Obama administration. When he did so, the crowd’s energy waned.
After the speech, Mr. Biden hugged the nuns, spent more than half an hour shaking nearly every hand at the rally and then boarded their bus, which was made to look like a campaign flier with the words “We the People, We the Voters” scrawled across the windows. He had a fund-raiser later in the day for congressional candidates, but first the bus dropped him off at the Waveland Cafe, one of Iowa’s best-known campaign stops.
Mr. Biden entered the diner and greeted a small group of local Democratic Party officials seated at a round table and eating cake with white frosting. He answered a question from reporters about Iraq, slipped his credit card to the waitress and, as his aides bounced the press from the diner, took his seat in the middle of a table full of nuns. They ordered burgers and Reuben sandwiches. Mr. Biden ate French toast with peanut butter and maple syrup. Then, for an hour and a half, he shared his views with them on subjects both theological and temporal, including St. Thomas Aquinas, the political origins of papal infallibility and the fallout from the sexual abuse scandal in the church.
He told the sisters that nuns had built his confidence as a stuttering child — “You have no idea of the impact that you have on others,” he said — and that he believed Francis was working hard to bring about reconciliation with them. “Everything will be all right,” he assured the nuns.
After a brief pause, Mr. Biden, who has run unsuccessfully for president twice, added that he had not “always accurately predicted everything.”
A version of this article appears in print on September 18, 2014, on page A22 of the New York editionwith the headline: Biden, a Catholic School ‘Kid,’ Praises Nuns Under Fire From the Vatican.