Joe Biden just loves nuns. "You're looking at a kid who had 12 years of Catholic education," the vice president said with a grin at this week's kick-off event for the third "Nuns on the Bus" national tour run by Network, a Catholic lobby group based in D.C. The sisters will travel 5,252 miles and visit 36 cities as part of a push to register voters and encourage participation in November's midterm elections. For a lifelong politician raised in the Church, a political rally with a bus full of sisters is a dream; after all, nuns "are more popular than anybody else," Biden observed.

But popularity isn't always enough in the Church. In 2012, American sisters whose orders are represented by the Leadership Conference of Women Religious (LCWR) were censured by the Vatican for, among other things, writing letters to the Holy See that suggested the "sisters collectively take a position not in agreement with the Church’s teaching on human sexuality" and having "a prevalence of certain radical feminist themes" in some of their programs and presentations. The LCWR represents 315 orders, or roughly 80 percent of the women religious in the United States; it is often considered less conservative than America's other major organization of sisters, the Council of Major Superiors of Women Religious. Two years ago, the Vatican's Congregation for the Doctrine of Faith ordered a formal review of the LCWR. Last spring, it decided that anyone who participates in any of the organization's events has to be vetted by Seattle Archbishop Peter Sartain, the secretary of the Church's representative body in the U.S., the United States Conference of Catholic Bishops. He declined to be interviewed for this article.

This is the tension of being a politically active nun in the United States: Women religious are caught between what they see as a call to serve their vocation and condemnation from the religious authority they follow.

“I don’t think anyone who’s called by God has an option about being political active," said Sister Ann Scholz, the LCWR's associate director for social mission. “Like Jesus, if we’re going to follow him in our vocation, we’ve got to be willing to be intimately involved in the world—and that includes a political reality.”

But it's tricky for sisters to determine exactly how they should fit into the American political landscape. Scholz said every order has a particular charism, or calling, for their work—many are involved in education, health care, etc. But American nuns have beenincreasingly outspoken about social justice since the 1960s—other orders focus more broadly on issueslike serving the poor and reaching out to new immigrants, which have both been the focus of past Nuns on the Bus tours.

But Vatican leaders object that the LCWR "is silent on the right to life from conception to natural death, a question that is part of the lively public debate about abortion and euthanasia in the United States"—women's issues, in other words.

Simone Campbell, a member of the Sisters of Social Service who organizes the Nuns on the Bus campaign, has vocally pushed back against the Vatican's perspective. "Helping women choose to carry their babies is all about economics," she said in an interview. The bigger question is whether women can "get health care and feed their kids .… There are so many ways we could support women rather than criminalizing [abortion]."

Although the leaders of the LCWR have been hesitant to discuss the Vatican's censures with the press, Campbell said she thinks the Vatican pushback is all about politics. "The real reason my organization got named in the censure is because we went in on health care," she said, referring to a letter she and other religious sisters submitted to Congress in support of the Affordable Care Act in 2010. In contrast, the United States Conference of Catholic Bishops opposed the legislation because of its contraception-coverage requirements. "Politics is being played way above our heads," Campbell said.

Although Scholz said it's uncommon for religious orders to align themselves with any political party, Campbell spoke at the 2012 Democratic National Convention, and past Nuns on the Bus tours have aligned with Democratic issues like aid to the poor and immigration reform. She hinted that the censure of the LCWR was being pushed by certain "players" in the Vatican who hold conservative views on reproductive issues. "I want to protect life, not some political ideology," she said.

"I'm not giving up the call of the work with the poor."

But for nuns, it's not an option just to board a bus and ignore the men in Rome. The Church is these women's lives. All sisters take a vow of obedience when they enter consecrated life. "Originally, it was extremely painful and extremely shocking," Campbell said of the censure. "I felt surprised, and maybe even a little betrayed. This month, I celebrate 50 years of being part of my community—that’s my life! To have somebody say we did it wrong ..."

But ultimately, she said, the Vatican's pushback hasn't changed much. "Things are painful only when they hold an element of truth. It’s not that personal pain, because I know that I've been faithful to the Gospel. It’s sad and it’s disappointing, but I'm not giving up the call of the work with the poor." Although it's still unclear what the final outcome of the LCWR review will be, the original document outlining the reasons for the review did state that bishops would be weighing the LCWR's affiliation with certain partner organizations—including Network.

As the entire Church turns its focus to issues of family, sexuality, and life preservation in its October synod, or assembly of bishops, there may be renewed pressure on women religious to shift their focus toward social issues. Although it's unclear what will come out of the synod, "certainly, what happens in the Church has a huge bearing on women religious, because it’s our church," said Scholz. “As congregations try to discern what social issues they’re going to address, that would be part of that discernment.”

She pointed to teachings of Gaudium et Spes, the pastoral constitution on "the Church in the modern world" that was written during the Second Vatican Council in the early 1960s. "We have an obligation to be involved in the griefs and anxieties, the hopes and joys of the people of God," she said. "We’re all called to build up God’s kingdom, right here, right now—not in the afterlife."