Sweeping into office in 2009, President Barack Obama captured near rock-star status around the world among millions who saw him as the embodiment of a new sense of social purpose. Now, that baton has largely been passed to Pope Francis, whose visit to the White House next month will put his common cause with Obama on vivid display.
Obama has made no secret of his affection for the outspoken pope, calling him a "transformative leader" whose influence has transcended the Roman Catholic community. The pope has embraced many of the issues Obama has sought to advance, including global warming, poverty and diplomacy with Iran and Cuba.
Vice President Joe Biden, a Catholic, said the pope's Sept. 23 visit will mark an important moment not only for Catholics but for all Americans.
"Pope Francis has breathed new life into what I believe is the central mission of our faith: Catholic social doctrine," Biden said in a statement to The Associated Press. Invoking key elements of Obama's agenda, Biden added that Francis "has become a moral rudder for the world on some of the most important issues of our time, from inequality to climate change."
The pope's brief visit to the White House is part of his highly anticipated trip to the U.S. and Cuba. It's a reunion of sorts for Obama and Francis, who first met when the president visited the Vatican last year.
Despite deep differences on some social issues such as abortion, Obama and the pope are expected to focus on areas of agreement. The White House said economic opportunity, immigration and refugees, and protection of religious minorities were high on the agenda.
"It's going to be a come-to-Jesus moment - no pun intended - for the many politicians who want to claim the mantle of Pope Francis," said Michael Wear, a former White House official who led faith outreach for Obama's 2012 campaign.
For Obama, the visit offers a chance to imbue his remaining goals with a sense of moral authority as he approaches the end of his presidency.
Viewed as largely above politics, Francis is extremely popular in the U.S. Tickets to his speech to Congress are such a hot commodity that an overflow crowd of thousands is expected to watch on Jumbotrons from the National Mall.
"In a way, Pope Francis has become a conscience for this age of the world. When President Obama came to office, he too had that aura for at least the first couple of years," said Stephen Schneck, who runs the Catholic politics institute at Catholic University of America. "But Pope Francis' message is moral and religious. He's not going to be talking about legislation."
The White House has praised Francis for involving himself in issues usually left to politicians. In a rare move, Francis personally intervened to help the U.S. and Cuba restore relations, writing leaders of both countries and hosting their delegations at the Vatican for final talks. And on climate change, a cornerstone of Obama's desired legacy, Francis added the weight of the pulpit by publishing a landmark encyclical calling climate change real and man-made.
Yet there are risks for Obama if he glosses over other, stark differences in views.
When he visited Francis early last year, Obama contradicted the official Vatican account of their meeting by saying they hadn't discussed social issues in any detail. Papal aides insisted the two leaders indeed discussed religious freedom, life and conscientious objection - buzzwords for abortion, birth control and parts of Obama's health care law.
"That's the delicate dance," said Julian Zelizer, a presidential historian at Princeton University. "The idea is to point out common areas of concern, rather than say, 'We are total allies.'"
Gay rights presents another area of likely disagreement. The pope's U.S. visit is focused on family issues, and while Francis has emphasized compassion and tolerance for gays and lesbians, he's also affirmed the church's opposition to same-sex marriages - putting him at odds with Obama.
The president's relationship with the Catholic Church has a mixed history. He won the Catholic vote in his presidential campaigns, according to exit polls - a feat even then-Sen. John Kerry, a Catholic, couldn't pull off. And when Obama signed his landmark health law in 2010, he gave the nearly two-dozen pens used to advisers and supportive lawmakers - but set aside one for Sister Carol Keehan, president of the Catholic Health Association, who played a key role in building support for the bill.
But the U.S. Conference of Catholic Bishops opposed the legislation over provisions on coverage for abortions and birth control. Hundreds of Catholic groups and employers sued the Obama administration over the law, claiming it infringes on religious freedom.