The improbability of a pope standing before a joint meeting of Congress comes in an era of wider acceptance of the Catholic faith as it intersects with public life and U.S. politics, and indicates a comfort level between the two that wouldn't have been imaginable several decades ago, observers said.
Times have changed whereby politicians do not have to wall off their faith from the office they hold, unlike how President John F. Kennedy had to defend his Catholic faith more than half a century ago, said Jesuit Father Christopher Collins, assistant professor of theological studies and head of mission and identity at Jesuit-run St. Louis University.
"More and more there seems to be a willingness for people being out front with their religious commitments while in public office, for both Democrats and Republicans," Father Collins told Catholic News Service.
"We are in a new phase of that and that is a good thing," he said. "It is a kind of a moving along the spectrum from privatization to a coherent synthesis of the faith of those who serve in public office."
Pope Francis' speech to Congress -- where about 30 percent of lawmakers are Catholic -- may be the most closely watched of the pope's talks during his visit Sept. 22-27 to Washington, New York and Philadelphia.
The pope also is scheduled to meet with President Obama at the White House and before heading north to give a separate address at the United Nations in New York and joining an interfaith service set for the Sept. 11 memorial at ground zero.
Father Collins, who sees Pope Francis as a continuation of the public advocacy efforts of his predecessor and St. John Paul II, said the pope's emerging theme on public policy issues is that the Christian faith should impel civic engagement regardless of the difficulties and risks.
"That has been a consistent theme with (Pope Francis): to get out of your complacency and let the church serve as a field hospital, and that you only become sick as a person or as a church when you turn in on yourself," he said, citing some of the pope's descriptions of the church's work in the world.
"This pope urges us to bring our faith out into the streets even though that gets messy and even though it can be a confusing place," Father Collins added. "That is the nature of the Christian faith."
Melissa Moschella, assistant professor of philosophy at The Catholic University of America, told CNS that the pope has the opportunity to make a stronger impact than previous popes who visited the U.S. because of his awareness of the media and wide global popularity.
"He has a simple, down to earth style, a warm, compassionate approach that people find very attractive. His style and way of talking about things really does radiate the joy of the Gospel," said Moschella, who will moderate a panel discussion on the history and practice of marriage at the World Meeting of Families in Philadelphia during the pope's visit.
Through his appointments of cardinals from smaller nations and underrepresented regions, the pope has shown that the church must be inclusive and consider a wide range of views, Moschella explained.
"You see him streamlining church governance and structures, financial management. Through example, he encourages public leaders to be servant leaders: not in it for their own ego, or personal advantage or agenda, to see themselves as servants of society and focus on the common good," she said.
Increasingly, Catholics in America appear compelled to public service despite the challenge of a spectrum of church teaching which refuses to fit neatly into any U.S. political party platform. But what bearing does church doctrine and Catholic social teaching have on a career in public life?
Pope Francis has expressed the view that politics is a worthy vocation, according to John Carr, director of the Initiative on Catholic Social Thought and Public Life at Georgetown University.
"We have lots of Catholics who have taken up that vocation, and increasingly Catholics are leaders of both the Democratic Party and Republican Party," Carr said.
Noting that there is no such thing today as "a Catholic vote," Carr said that Catholic voters are influential in elections as perhaps "the ultimate swing vote."
"The bad news we are more Democrats or more Republicans than we are Catholic," he said. "We ought to see a more consistent concern for life, and I hope Pope Francis will ask us to be more clear in our care for the poor, the unborn and the undocumented.
"I think Pope Francis will affirm our leaders and make them profoundly uncomfortable at some moments."
He noted that Pope Francis' Jesuit-inspired leadership style and personal priorities will be highlighted by a meeting with homeless people following his speech to Congress.
"He looks at the world from the bottom up. When he had a day off, he would go to the slums instead of the football game or to the opera, and he will bring that (sensibility) to the papacy and to Washington," Carr said. "This is not the center of his world."
It seems it is Congress that needs advice from the pope, and that says something about the times we are in, Carr said, suggesting that he hopes the legacy of Pope Francis' visit will be to "get people out of ideological boxes and think and act anew."
"I think he will challenge our consciences at a time when we really need it."