Father Marcelo Rossi, Brazil's Celebrity Priest

LAL DE ALMEIDA /The New York Tim

Trim and tidy in a worn white blazer, his hair cut for Sunday, José Batista da Silva kneels on the cement floor and prays. The 56-year-old former bus driver knows every hymn at the Sanctuary of the Byzantine Rosary, Father Marcelo Rossi's Catholic megachurch in São Paulo, where he has attended mass for the past six years. Today he is hoping for a little extra blessing.

Batista's head is bowed and his arms stretch toward the skylight. In each hand he grasps a pocket-size passbook, the document Brazilians use to register employment contracts. Both he and his daughter Samanta, age 23, are out of work, and Batista, who sustained a back injury on the job, saw his disability pension cut in 2007. But among the 10,000 faithful who have gathered here to worship, sway, and bear witness as Father Marcelo sets the gospel to song, he draws comfort. "Everyone prays and sings. Here, it feels like God opens His heart a little wider to us," he says. "Father Marcelo is bringing back people to church."

Charismatic priests such as Rossi have retained congregants with singing, chanting, and gospel rock. AFP

That is the sort of message Rome is keen to hear. When Pope Francis touches down in Brazil on July 23, the world will be watching. Officially, his visit is to kick off World Youth Day, a weeklong pilgrimage held in a different country every three years that draws devout Catholics from around the world. Yet Francis's first major international journey is freighted with significance for a church in turmoil. Roiled by pedophilia scandals and financial mismanagement, pulled down by outdated liturgy, and facing a global shortage of priests and nuns, the 1.2 billion–strong Roman Catholic order is losing souls in droves.

In Brazil, nominally the world's largest Catholic country, the church's struggles have provided an opening for Protestant evangelical sects, whose fast-talking televangelists woo away the poor and the forgotten into jerry-built temples that have spread like fast-food franchises. This is where Father Marcelo and his megachurch come into play. The 46-year-old preacher and author (one of his self-help-style books is currently the bestselling title in Brazil) is at the vanguard of a Catholic counterinsurgency that aims to make Brazil's church more appealing by taking cues from the rollicking approach of the evangélicos. "Most of our parishes are straight out of the fourth century. The liturgical style has not changed, and the people have strayed," Rossi says. And so he has shaken things up by introducing gospel rock, theatrical prayer sessions, and an all-out communications blitz that would impress Madison Avenue. "We cannot sit back and wait for people to come to church," he says. "The church has to reach out and bring people back."

Pope Francis’s first major international journey is freighted with significance for a church in turmoil. Camera Press/Redux

EARLY LAST century, two thirds of Roman Catholics lived in Europe. But now religiosity is moving east and south. Asia's Catholic flock now numbers 137 million and Africa's Catholics have more than tripled their ranks in the past four decades, rising from 45 million in 1970 to 176 million last year.

Rome's New World stronghold is still Latin America, home to 41 percent of global Catholics. So it's no surprise that the Argentine-born Jorge Mario Bergoglio, the church's first leader from the Americas, is kicking off his papacy by calling on Brazil. And yet here, too, the church is in trouble. Though Brazil's flock numbers 126 million—or 11 percent of the world total—the flagship faith has been struggling with attrition for decades. In a land where church spires once trumped skyscrapers, millions have strayed. Once, virtually all God-fearing Brazilians called themselves Catholics. Today, just two in three take their cues from Rome. Meanwhile, evangelical Protestants have seen their numbers soar 22 percent in the past decade, while the ranks of those with no allegiance to religion are growing even faster.

Rossi added aerobics steps to Sunday services and played lively music. Soon his small church was overflowing.

Hastening the exodus is a political and social upheaval of tectonic proportions. A strengthening democracy, rapid urbanization, and a flourishing consumer economy have shaken the country and awakened the flock to alternatives—spiritual and otherwise. Once-clandestine African spirit cults like Candomblé have become acceptable forms of worship, while Protestant evangelical sects have taken root by aggressively making their pitch to the poor and the forgotten.

Rome’s influence in Brazil has declined in recent years. Heeb/laif/Redux

Many of the new orders are Pentecostals, with beat-the-devil preachers who read the Bible literally and rail about the end of days. They pass the collection plate—often in the form of a gunnysack hooked on a stick—and dangle the promised redemption to those willing to empty their pockets. Sometimes the hard sell is scandalous. One pastor was notoriously captured on a video—which subsequently spread via YouTube—browbeating a penitent for not divulging the PIN for his debit card. "That's no fair," said Assembly of God Pastor Marco Feliciano of the reluctant worshiper. "He's going to ask God for a miracle and God won't deliver, and then he'll say God is bad." (What's worse, Feliciano is a federal congressman who presides over the congressional human rights council and whose signature legislative initiative was a bill to promote therapy to "cure" homosexuals.)

And yet the born-again message has played well in the favelas, the local shantytowns. Preachers have set up their storefront temples in the slums, opening their doors to alcoholics, addicts, and lapsed Catholics for whom the turgid centuries-old liturgy had long ago lost its charm. I once followed a group of young evangelical missionaries into the combat zones of Rio's drug wars, where they prayed for the souls of teenagers with AK-47s.

The evangelicals also understood something essential: that today's worshipers want their Sundays infused with drama and pageantry. Mass baptisms, exorcisms, thundering oratory, and speaking in tongues are liturgical staples. Some of the fastest-growing orders have invested heavily in neon-lit temples and set their sermons to electric guitars and crashing drums, bringing the faithful to their feet. And those who can't go to church turn on their television sets, where the televangelists have been buying up time slots. One major competitor to the Catholic monopoly, the Universal Church of the Kingdom of God—a Pentecostal order run by the fire-breathing Edir Macedo—bought an entire television station with a nationwide audience.

PADRE ROSSI started preaching in the late 1990s, when Brazil's bishops were rubbing their rosaries over the waning congregations. Part of the problem was that church hierarchy was still arguing over liberation theology, in which politically minded clergy mixed Christian doctrine with Marxism and declared that their mission was redeeming the poor. The ideological brawl left many Catholics cold and encouraged them to stray.

The church's answer was the Charismatic Revolution, a movement of young priests like Rossi who infused their sermons with singing, chanting, and gospel rock. For Rossi, with a degree in physical education, it was the perfect repertoire. Athletic and strapping, standing a muscular 6 foot 5, he added aerobics steps to Sunday services and played lively music. Soon his small church in a blue-collar São Paulo district was overflowing.

Many of the devout wear T-shirts emblazoned with pictures of the pop padre himself.

This style drew criticism both from progressives and conservatives within the church. "They don't like me very much," he says, enigmatically. "Many charged I was alienating people by emphasizing emotions. But in faith you have to have both sides, and you can't ignore emotions."

Rossi eventually built a new church—the Sanctuary of the Byzantine Rosary, a giant warehouselike structure looming on the city outskirts that seats 8,500 with room for a few thousand more standing at the back. Every Sunday, caravans of worshipers arrive in chartered buses to watch Ross stride and strut the lofty dais while leading the congregation in prayer. He often ends meetings by dousing the crowds with buckets of holy water.

Catholics have already begun preparing for the pope’s arrival for World Youth Day in Rio de Janeiro. Globo

Many of the devout wear T-shirts emblazoned with pictures of the pop padre himself, while others grasp signed copies of Rossi's two ultrapopular books, which retell passages of the Bible in simple, bite-size chapters. Kairós (Greek for "God's timing") is Brazil's current bestseller, and his 2010 book, Ágape (meaning "divine love"), a stripped-down version of St. John's gospel, sold 8.4 million copies—shattering all national publishing records for a single title. Sales from these books, plus the take from Rossi's gospel CDs and the DVD of his popular film, Maria, Mother of God, have reaped more than $10 million. He plows all of it back into his new church, where there's not a collection plate in sight. "Why should I ask for money if I am able to work?" he says.

And work, he does. With a daily radio program to host, book signings to attend throughout Brazil, and Sunday masses that draw crowds that rival rock concerts, Brazil's pop padre can barely sit still. All the better for Pope Francis, who arrives in the world's biggest Catholic nation this month, with a country to enchant and Rome's authority to mend.