"We look forward to welcoming you to our workplace and request the opportunity to meet you." Pope Francis is known for holding ad hoc meetings with the poor and bereft; even so, the invitation he received from 46 disgruntled canteen workers at the U.S. Capitol, ahead of his visit there on Sept. 24, was audacious. The Bishop of Rome does not mediate in petty pay disputes.

Yet the stunt illustrates a striking reality of Pope Francis's planned five-day visit to his American flock, the richest and fourth-most-populous of any nation. From aggrieved Hispanics to irate conservatives, from an increasingly questioning Catholic rank-and-file to the many non-Catholics attracted to the pope's blend of modesty and celebrity, millions of Americans want a piece of him.

Not even John Paul II's hugely popular visit to America in 1979, when the U.S. church was smaller yet stronger than it is today — with over 20,000 more priests — excited more hoopla than has the looming prospect of Pope Francis. In Catholic churches, schools and hospitals across Washington, D.C., New York and Philadelphia, destinations for his first trip to America, life-size cutouts of the Argentine priest are being set out and posters unfurled. At the open-air mass he will say in Philadelphia, up to 1.5 million people are expected.

And what the pontiff says, including in the first papal address to Congress and another outside Independence Hall, birthplace of the Constitution, will carry unusual political weight. Because the political context into which he will step, for Catholics, non-Catholics and especially the 55 million Hispanics who increasingly dominate the American church, is fraught.

Though far more vigorous than any dwindling European equivalent, the American church badly needs a shot of the "Francis effect" — the institutional pick-me-up Catholics have looked for in the pope's popularity. The financial and reputational damage done by revelations of thousands of child-abuse scandals has exacerbated deeper and daunting changes, including a hollowing-out of what were once pre-eminent congregations, in New York, Philadelphia, Chicago, Boston and other centres of European Catholicism, as their members move to the suburbs, or simply quit.

A recent survey by the Pew Research Center suggests that for every American converted to Catholicism, six abandon it — easily the highest net loss of any church. Around 13 percent of adult Americans are former Catholics — if they were a denomination, it would be America's third-biggest.

The outflow is largely covered by the increase in Hispanic Catholics, who now represent over a third of the total, and rising fast. This is injecting hope and dynamism into an institution that would otherwise be in decline. "We do funerals, they do baptisms," quipped John Carr, a Catholic thinker at Georgetown University in Washington. Yet the change is not without friction.

Hispanicization is shifting the church's center of gravity to the south and west and changing its culture, including the language of worship, almost everywhere. "This Easter we had three crosses outside our church with actors on them," said Carr. "That's not how we usually celebrate Good Friday." Of eight special masses being said for the pope in the capital, where he will also canonize America's first Hispanic saint, five will be at least partly in Spanish, the language in which the pontiff will deliver most of his addresses.

General enthusiasm for the pope, whose approval rating among Americans is in the high 80s, is a fillip for all Catholics. But at a time when the front-runner for the Republican presidential nomination, Donald Trump, suggests spoken Spanish has no place in American public life, El Papa's visit is especially reassuring for Hispanics. "The pope is sending a message that you need to be welcomed if you speak other languages, that language should not be an issue,' says Father Evelio Menjivar, a Washington-­based parish priest who is organizing the Spanish-language celebrations.

Francis will address Congress in English, but that will not lower the political temperature in a place where Catholics have never been more prominent. Fifty years ago, John Kennedy, America's only Catholic president, saw his presidential campaign dogged by claims that it was impossible to serve both America and Rome. Eight Catholics are now vying to be president — including Jeb Bush for the Republicans and (perhaps) Joe Biden for the Democrats. Almost a third of the House of Representatives is Catholic — including the Republican speaker, John Boehner, at whose invitation the pope will make his address.

This does not mean he is about to swing the election: Catholics vote in line with all Americans — which is to say, white ones lean Republican and Hispanic ones Democratic. Yet the rise of Catholic politicians has brought into focus the wearisome degree to which the church's main split, between an ascendant conservative wing that worries mainly about religious freedom and the rights of the unborn, and a liberal wing more concerned with social justice, has become a proxy for America's wider political brawl. That will make the pope's address inevitably politicized and acutely sensitive.

A champion of poor immigrants, a critic of capitalism and a tree-hugger who has, meanwhile, done little to revise the church's social teachings, Francis has something for both camps. So both are claiming him — "the degree to which everyone wants this guy on their team is remarkable," said George Weigel, a conservative Catholic commentator. Yet right-wing Catholics are the more uneasy. "People quite close to the pope misunderstand America or don't like America," said Robert Royal, another conservative commentator. "I'm worried about that."

There will be more such grumbling, not least because the pope is expected to speak on immigration and the environment early in his visit, before issuing a defense of the traditional family, at a summit in Philadelphia, later on. Yet any suggestion that the pope is himself anti-American is hard to back up. He is a critic of the greed and economic fragility capitalism can engender; less obviously of the system itself. That is a position that has long been taken, if more quietly, by American bishops, as indeed is the pope's concern for poor immigrants and the environment.

As a son of European immigrants, his biographer Austen Ivereigh noted, the pope's personal history is also distinctly American: "He's the first pope of the New World." And in his efforts to decentralize power from the Vatican, he has perhaps done more to dismantle his office's thoroughly un-American monarchic pretensions than any of his predecessors.

The real target of his papacy, argued the Rev. Matt Malone, a fellow Jesuit and editor of America magazine, is just the sort of polarization awaiting him on Capitol Hill. "Both sorts of cultural warrior, on the left and the right, think the pope is aligned with them or against them, but what he's really saying is: 'A pox on both your houses.' He is reminding us that our goal as Christians is not to be right, but to be holy."

It is an attractive message. But to endure the political pummeling, from left and right, that the pope's every utterance is about to attract, he may need a miracle.