Capitol Hill is consumed by disputes over abortion and federal funding for Planned Parenthood after hidden-camera videos showed its officials talking about the organization's practice of sending tissue from aborted fetuses to medical researchers. While Francis has staunchly upheld church teaching against abortion, he has recently allowed ordinary priests, and not just bishops, to absolve women of the sin.
Francis' visit comes three months after the U.S. Supreme Court legalized same-sex marriage, putting U.S. bishops on the defensive and sharply dividing Americans over how much they should accommodate religious objectors. The pope has strongly upheld church teaching against same-sex marriage but adopted a welcoming tone toward gay people themselves, saying, "Who am I to judge?" when asked about a supposedly gay priest.
Americans are also wrestling anew with issues of racism. A series of deaths in recent years of unarmed black men at the hands of law enforcement has intensified debate over the American criminal justice system. Francis will see that system up close when he meets with inmates at a Pennsylvania prison.
U.S. bishops, meanwhile, expect Francis will issue a strong call for immigration reform, a subject that has heated up with hardline anti-immigrant rhetoric from some of the Republican presidential candidates, especially Donald Trump.
Francis, the first Latin American pope, will be sending a powerful message on that front by delivering the vast majority of his speeches in his native Spanish.
"Our presidential candidates have been using immigrants as a wedge issue," Miami Archbishop Thomas Wenski said. "It's our hope that the visit of Pope Francis will change this narrative."
Francis' most eagerly watched speech will be his address Thursday to Congress. Republicans and many conservative Catholics have bristled at his indictment of the excesses of capitalism that he says impoverish people and risk turning the Earth into an "immense pile of filth." Many conservatives have likewise rejected his call for urgent action against global warming.
Nevertheless, Francis enjoys popularity ratings in the U.S. that would be the envy of any world leader. A New York Times/CBS News poll conducted last week found 63 percent of Catholics have a favorable view of him, and nearly 8 in 10 approve the direction he is taking the church.
Just how far Francis presses his agenda in Washington is the big question.
Paul Vallely, author of "Pope Francis, The Struggle for the Soul of Catholicism," predicted both "warmth" and "some finger-wagging" from the pope.
"He won't necessarily confront people head-on," Vallely said, "but he'll change the priorities."
The Associated Press