Washington (CNN) America may be in for some tough love from the Pope.

After a lifetime of watching the world's most affluent and powerful nation from afar, Pope Francis walked on U.S. soil for the first time Tuesday, at the age of 78, when he arrived in Washington from Cuba.

He's assured of a warm welcome from millions of U.S. Catholics, and his poll numbers -- which would be the envy of any politician -- suggest that curious adherents of other faiths and even the nondevout are also eagerly awaiting his visit.

Don't miss live coverage of Pope Francis' trip to the U.S. on CNN and CNNgo , and see the people and places that shaped Pope Francis in a CNN special report, " The People's Pope ," tonight at 9 p.m. ET.

But the first Latin American pope's blessings on America could also contain uncomfortable challenges as he addresses a country that encapsulates many of the ills he has denounced as the head of one of the world's largest religions. Though there are aspects of American life that Francis embraces, he has quickly become known for blunt critiques of contemporary society and global economics, and his criticism -- from capitalism to climate change to technology -- spans the political spectrum.

"Pope Francis is the ultimate Washington outsider. His priorities are not Washington's priorities," said John Carr, director of the Initiative on Catholic Social Thought and Public Life at Georgetown University. "We think we are the center of the world. We are not the center of Pope Francis' world. He is frankly more comfortable in the slums of Argentina than in the corridors of power."

From the flurry of encyclicals, writings and other commentary that Francis has issued since his election two years ago, the United States, home to the world's mightiest market economy, a ravenous consumer culture and nurturer of the World Wide Web, appears to represent much of what he abhors.

The Pope's political challenge

That's why Francis faces a delicate political assignment as he meets President Barack Obama and addresses Congress, in addition to holding masses and other public events in Washington, Philadelphia and New York this week.

Francis is stepping into an intense domestic debate on issues close to his heart, including income inequality, climate change, abortion, the definition of marriage, religious freedom and immigration. Rival politicians are sure to exploit his visit for their own purposes, and the messages he imparts could potentially reshape how those issues figure in the presidential campaign.

One reason he may have little to lose: Unlike the lawmakers whom he will stand before during the first-ever address to a joint meeting of Congress by a Pope, Francis is accountable only to his faith and the Gospel and so is unlikely to hold back for political reasons.

"He is coming to the richest country in the world. I believe he is going to challenge us to say with that comes great responsibility," said Rudy Lopez, executive director of Interfaith Worker Justice.

Many observers expect Francis to implicitly rebuke Republicans -- some of whom deny a link between human behavior and climate change, a topic which he addressed in an encyclical in June -- for their reluctance to tackle global warming. The Pope may also wade into the raging debate about immigration in the United States, after warning earlier this year that nations that close the door on migrants should seek God's forgiveness.

But he's going to be an "equal opportunity disturber," said Rev. James Martin S.J., editor at large for America magazine, the journal of U.S. Jesuits.

Differences with Democrats

Democrats could find themselves criticized for support of abortion and same-sex marriage, policies that conflict with the doctrine of the Catholic Church.

And the gesture Francis will make by going directly to lunch with homeless people rather than with his congressional hosts after his speech on Capitol Hill will resonate on both sides of the aisle.

"He is a walking, talking parable," said Carr. "This is a Pope who looks at the world from the bottom up and from the outside in. I think he brings to Congress and the White House a different perspective than they are used to hearing."

And that perspective could be galling for both parties.

"The role of the Christian is to comfort the afflicted -- of course -- but also to afflict the comfortable. We have people who need to be afflicted a little bit, particularly in their outlook towards the poor and the marginalized," said Martin.

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Although the Pope hasn't articulated a clear view on the United States since being elected, much commentary has been devoted to his Argentine roots and whether he adheres to a Latin American worldview that is suspicious of the United States and aggressive capitalism.

But Francis is unlikely to openly wag a finger at the United States. His criticisms could be bold, but they will be implicit -- possibly in one of his famous digressions from his prepared text -- and they will be delivered with grace and civility.

"He is a good teacher," said Cardinal Timothy Dolan, the archbishop of New York, on CNN's "New Day" on Monday. "He knows one of the more effective ways to teach is to reaffirm what is good, to congratulate us on what we are doing well."

For instance, he is likely to praise American liberty, democracy, opportunity and religious and racial plurality.

"When you do that, a savvy person says, 'Boy, that's sure good of him that he is affirming what we do good. But on the other hand, are we doing it as well as we should?' '" Dolan said. "There's where the examination of conscience comes in."

High approval ratings

But while Francis is almost universally praised for his personal example of humility and the way he lives his faith -- his approval rating in the U.S. was at 59% in a Gallup poll in July -- he's also attracted plenty of criticism here.

His progressive political views on many issues -- well to the left of any major U.S. political figure -- are often criticized as those of a naif straying out of his lane, and conservatives say he misunderstands the role of free enterprise in lifting millions of people around the world out of poverty.

His June encyclical provided a blistering critique of rich countries' energy consumption and their role in climate change, which he labeled "one of the principal challenges facing humanity in our day."

Photos: Pope Francis visits Cuba Photos: Pope Francis visits Cuba Security surrounds Pope Francis as makes his way to the Metropolitan Cathedral in Santiago, Cuba, on Tuesday, September 22. The Pope arrived in Cuba on Saturday and is scheduled to travel to the United States on Tuesday. Hide Caption 1 of 23 Photos: Pope Francis visits Cuba Pope Francis prays inside a sanctuary in El Cobre, Cuba, on Monday, September 21. Hide Caption 2 of 23 Photos: Pope Francis visits Cuba Residents wait for Pope Francis to drive past in Holguin, Cuba, on September 21. Hide Caption 3 of 23 Photos: Pope Francis visits Cuba The Pope celebrates a Mass in Holguin on September 21. Hide Caption 4 of 23 Photos: Pope Francis visits Cuba Pope Francis, left, blesses the communion bread during the Holguin Mass on September 21. Hide Caption 5 of 23 Photos: Pope Francis visits Cuba People cheer in Holguin as Pope Francis arrives for the Mass on September 21. Hide Caption 6 of 23 Photos: Pope Francis visits Cuba Pope Francis stands with Cuban President Raul Castro in the Revolution Palace in Havana, Cuba, on Sunday, September 20. Hide Caption 7 of 23 Photos: Pope Francis visits Cuba Pope Francis shakes hands with Fidel Castro in Havana on September 20. The Vatican described the 40-minute meeting at Castro's residence as informal, with an exchange of books. Hide Caption 8 of 23 Photos: Pope Francis visits Cuba Pope Francis walks to the altar to celebrate Mass at Revolution Square in Havana on September 20. Hide Caption 9 of 23 Photos: Pope Francis visits Cuba An enormous crowd fills Havana's Revolution Square for the Pope's Mass on September 20. Hide Caption 10 of 23 Photos: Pope Francis visits Cuba Pope Francis blesses the Virgin of Charity as he celebrates Mass on September 20. Hide Caption 11 of 23 Photos: Pope Francis visits Cuba Pope Francis kisses a child as he arrives in Revolution Square on September 20. Hide Caption 12 of 23 Photos: Pope Francis visits Cuba Crowds surround the Pope as he arrives in Revolution Square on September 20. Hide Caption 13 of 23 Photos: Pope Francis visits Cuba Pope Francis arrives at Revolution Square on September 20. Hide Caption 14 of 23 Photos: Pope Francis visits Cuba Worshippers in Havana gather before sunrise for the Pope's Mass on September 20. Hide Caption 15 of 23 Photos: Pope Francis visits Cuba Women wave from an apartment building as Pope Francis travels from the airport on Saturday, September 19. Hide Caption 16 of 23 Photos: Pope Francis visits Cuba Pope Francis waves to people as he arrives at the Apostolic Nunciature in Havana on September 19. Hide Caption 17 of 23 Photos: Pope Francis visits Cuba Crowds line the streets to greet the Pope in Havana on September 19. Hide Caption 18 of 23 Photos: Pope Francis visits Cuba Pope Francis speaks with Cuban President Raul Castro during his arrival ceremony on September 19. Hide Caption 19 of 23 Photos: Pope Francis visits Cuba Soldiers march inside the airport in Havana during the arrival ceremony for the Pope on September 19. Hide Caption 20 of 23 Photos: Pope Francis visits Cuba Children welcome the Pope shortly after he landed at the airport on September 19. Hide Caption 21 of 23 Photos: Pope Francis visits Cuba Cuban President Raul Castro walks with the Pope after his arrival on September 19. Hide Caption 22 of 23 Photos: Pope Francis visits Cuba Pope Francis' cap flies off his head as he deplanes in Havana on September 19. Hide Caption 23 of 23

In the same document, he also blasted social media, in a message that can make for uncomfortable reading in the nation that gave the world the iPhone, Google, Facebook and Twitter: "When media and the digital world become omnipresent, their influence can stop people from learning how to live wisely, to think deeply and to love generously."

And he has reserved some of his harshest language for capitalism as it is practiced in the United States and elsewhere.

"An unfettered pursuit of money rules. The service of the common good is left behind," he said at a conference in Bolivia in July. "Once capital becomes an idol and guides people's decisions, once greed for money presides over the entire socioeconomic system, it ruins society, it condemns and enslaves men and women, it destroys human fraternity."

Six of the current GOP presidential candidates, including Jeb Bush, Marco Rubio and Chris Christie, are practicing Catholics. They have all said that while they take their religious teaching from the Pope, they look for political guidance elsewhere.

Cuba on the agenda

Much of Obama's agenda, in comparison, fits more comfortably with the Pope's positions. The Pope was influential, for instance, in brokering Obama's recent opening with Cuba, and the President has referenced the Pope's remarks in his own warnings about the dangers of economic inequality.

But the administration also has its differences with the Pope. The President has been criticized for inviting an openly gay Episcopal bishop and several gay activists to a White House welcoming ceremony for the Pope. And the Democratic Party's traditional support for abortion rights collides directly with Catholic doctrine.

So it is not only the GOP that is awaiting the Pope's message with some anxiety. White House officials admit they have no idea what he will say.

"The Pope is a very independent figure, and we know from his previous travels that we don't know what he is going to say until he says it," said Charles Kupchan, National Security Council senior director for European Affairs, which includes the Holy See.

Kupchan said he expected that there would be some elements of the Pope's message with which the White House would not concur.

But he added: "We are hoping that his moral authority helps us advance many of the items that we take to be very high on our policy agenda."