Pope Francis' favorability ratings in surveys of U.S. Catholics and all Americans have fluctuated in his two-year-old papacy — but always within a range that would be the envy of any leader.

His impending trip to the U.S. is already causing a frenzy. Free tickets for public events with the pope are being snapped up within minutes. Politicians, whether they agree or disagree with his views, are heading to Washington to see him. Yet, there is some trepidation about what the "slum pope," who has made the poor and vulnerable a focus of his papacy, will say to one of the richest countries in the world.

In polls by the Pew Research Center, Francis' popularity peaked in February 2015 at 90 percent among Catholics and 70 percent in the general public.

After he released his encyclical in June on ecology and climate change, calling for aggressive government action and personal moral transformation to save the planet and humanity, his approval ratings dipped. A Gallup poll found political conservatives upset he had gone so far — and liberals disappointed he hadn't done more.

Francis has said "Who am I to judge?" about a purportedly gay priest, but has upheld marriage as the union of a man and a woman.

He has called for more women in church leadership roles, but does not support ordaining them.

Still, a Public Religion Research Institute survey last month found his popularity returning to higher levels overall as his first U.S. visit neared.

"He acts more as a pastor than an authority figure," said John Thavis, former Rome bureau chief for Catholic News Service and author of "The Vatican Diaries." "He has a forceful personality. He's a man who looks happy, and he enjoys life and he enjoys people."

Here's a look at the impact Francis is already having in the U.S., before arriving Sept. 22 to visit Washington, New York and Philadelphia:

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FRANCIS THE PUBLIC FIGURE

In a politically polarized country like the U.S., Francis' effort to turn down the volume on the culture wars dismayed hardliners, but was a relief for many Catholics and those alienated from the church. Just months into his papacy, he told Jesuit magazines that while he was a "son of the church" who upheld Catholic doctrine, he believed the church was too focused on "small-minded rules" and should instead be a "field hospital" that showed mercy on the spiritual battlefield of the modern world.

He followed these proclamations with real-life gestures of compassion, such as hosting the homeless for a tour and meal at the Vatican museums, and adopting a comparatively stripped-down lifestyle for a pope — using an economy car and carrying his own travel bag. A photo of Francis embracing a badly disfigured man in 2013 at the end of a Vatican general audience has become emblematic of his papacy.

"He's come down from the papal throne," Thavis said.

It helps that Francis has a sense of humor and a skill for the memorable turn of phrase: Priests should be "shepherds living with the smell of the sheep." Vatican bureaucrats were suffering from "spiritual Alzheimer's." Consumers and corporations are turning the Earth into an "immense pile of filth." No special knowledge of Catholic teaching is required to understand his meaning, which amplifies his message in the U.S., where nearly a quarter of the population says they have no particular religion.

"The world today ... they have kind of a built in stethoscope to detect artificiality and they don't see any in this man," said New York Cardinal Timothy Dolan, who will host the pope. "They see a man who is utterly honest, who seems to have no fear and who just says things that are true with an immense love, with a simplicity, humility and sincerity that seems to captivate people. There's no script. There's no PR. There's no marketing. He's simply who he is."

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AFFLICTING THE COMFORTABLE

Francis remains popular despite discomfiting many inside and outside the church.

In July, Carl Olson, editor of the conservative Catholic World Report, wrote that while he agreed with some of the pope's critiques of society's ills, Olson also found a "weariness" among some Catholics over Francis' tone, which Olson described as sometimes "haranguing, harping, exhorting, lecturing" and "grating."

Francis' moral instruction about daily life — on the Christian duty to stop consuming so much, start spending more time with the poor and give up air conditioning for the sake of the environment — has left some feeling scolded.

"We have a pope who makes us, to put it bluntly, uncomfortable," Kurt Martens, a canon law professor at the Catholic University of America, said in a recent talk at the Council on Foreign Relations. "He asks questions about, 'What did you do for the poor?"

While Francis addressed his encyclical to "all people of good will" and didn't single out the U.S. or any other country, his condemnation of the global economic system and the "unfettered" pursuit of profit was viewed as especially targeting America, whose immense wealth and influence shapes how the world does business.

Greg Erlandson, president of the Catholic publishing company Our Sunday Visitor, who covered Pope John Paul II from Rome, said Francis, the first Latin American pontiff, is asking people to "examine our consciences" — and "examination of consciences really makes you uncomfortable."

"It's stressing everybody a little," Erlandson said. "We're really hearing a voice from the Southern Hemisphere. We're hearing from someone who has literally seen the world from a different perspective."

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UPENDING THE CHURCH

Francis' exhortation to throw open the doors of the church to all, then address their beliefs and behavior later, has unsettled many in American Catholic leadership. Using the metaphor of a badly injured man, Francis said, "You have to heal his wounds. Then we can talk about everything else."

Many U.S. bishops, while also striving to bring back fallen-away Catholics, had been putting doctrine first. The overwhelming majority were appointed by Popes John Paul II and Benedict XVI, who set the church on what they viewed as a badly needed course correction, establishing clearer, stricter boundaries for what could be considered truly Catholic.

Primary markers of Catholic identity became a person's position on marriage, abortion rights and related issues, said Paul Vallely, author of "Pope Francis, The Struggle for the Soul of Catholicism." U.S. bishops said they had no choice but to prioritize these concerns, as society and lawmakers came to accept policies the church considered immoral.

Francis talks about marriage and abortion, but with nowhere near the emphasis of his predecessors. Now, the pope is measuring Christian commitment according to how church members treat the poor, immigrants and the environment, Vallely said. The shift has sent some Catholic conservatives, who had insisted obedience to John Paul and Benedict was the duty of every authentic Catholic, parsing Francis' encyclical to decide what they can ignore.

"Francis is not a liberal. He's a very complicated character. He's got some liberal tendencies, but he's got some conservative tendencies too," Vallely said. "But he wants to shift the focus from sex to poverty."

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REBRANDING THE FAITH

Francis' revolutionary pontificate has drawn the spotlight away from controversies that have dogged the bishops and the U.S. church.

"We've needed for a while a renewed image, a renewed face of the church, and Pope Francis is giving it to us," Dolan said.

The Vatican under Francis quickly ended a contentious investigation of U.S. nuns that brought grief to the bishops.

When Benedict was pope, the Vatican ordered an overhaul of the largest association for U.S. religious sisters, the Leadership Conference of Women Religious, over alleged violations of orthodoxy, which the nuns denied. The investigation prompted a massive public outcry that stunned and heartened the sisters, and put conservatives in the church, including bishops, on the defensive. In the end, Vatican officials closed the nuns' case this year with no major changes ordered for the group and a thank you from Francis for the sisters' work.

Clergy sex abuse scandals persist in American dioceses, despite broad reforms by the bishops in 2002 that pledged a quick ouster for guilty clergy and more safeguards for children. Along with ongoing lawsuits in different states, three dioceses remain in bankruptcy court over abuse claims, and one, the Archdiocese of St. Paul and Minneapolis, is being prosecuted on charges of failing to protect children.

Advocates for victims argue Francis has created an impression of change while taking little concrete action to address the issue around the world. Francis formed an advisory committee on ending child molestation in the church, has met with victims at the Vatican and announced plans for a tribunal that aims to hold bishops accountable if they fail to stop abusers.

But public fascination with Francis, and the goodwill he has generated, has largely overshadowed these ongoing debates about what should be done next on the long-running scandal.