MESA, Arizona (Reuters) - For years, Nora Castaneda watched her Mormon community grow and grow as it drew converts from a burgeoning Hispanic population in Mesa, Arizona. Then, in 2010, it all went into slow motion.
It turned out the author of Arizona's tough illegal immigration law, then State Senator Russell Pearce, was a Mormon. As word got around, the dark-suited missionaries who'd been having great success in this Phoenix suburb were suddenly having doors slammed in their faces.
"Now we hardly have a baptism," Castaneda said.
The strongest growth for the Church of Jesus Christ of Latter-day Saints in recent years has come overseas, and one of its richest source of recruits in the United States is the Hispanic community.
As Arizona prepares to holds its Republican presidential primary Tuesday, tensions over immigration within the sizeable Mormon community are bubbling beneath the surface - in a way that could cause discomfort for candidate Mitt Romney, the on-again, off-again frontrunner.
Romney, a Mormon, has said the federal government should drop its legal case against Arizona's hardline law, and that the government should stop providing immigrants with "magnet" services that attract them, as well as enforcing the border. The Arizona Republic newspaper endorsed Romney, but said "his effort to position himself as the 'toughest' GOP candidate on immigration issues is a concern."
A Romney spokeswoman declined to discuss the Mormon church's stance on immigration.
For the moment, Romney's stance appears not to have dented his chances in Arizona - perhaps because his rivals are just as tough. Latest polls give him a comfortable lead in the state. But in a general election it may be a factor.
Mormons are only about 2 percent of the U.S. population, but they are politically active. Their support helped Romney win the primary in Nevada, a likely swing state in November.
The kind of hard line on immigration espoused by Romney and Pearce is jarring for many adherents of a religion that is growing more international and multicultural by the day.
Despite the popular perception of Mormonism as a white, conservative and uniquely American religion, the church has been changed from within by its own international ambitions.
As recently as the 1970s, the church still denied full privileges to black members, and its growing cadre of global missionaries largely avoided Africa in favor of Latin America.
But when recruits in Brazil began to trace their family histories, a rite of passage in the religion, there was a problem: many new Mormons found black ancestors, raising questions about a long-standing ban on blacks joining the lay priesthood.
The Mormon leadership did not know what to do, recalled historian Jan Shipps, a preeminent non-Mormon scholar of the religion. So the head of the church in 1978 took his top lieutenants into the temple and waited for a sign from God. Three days later, the church's prophet described his revelation: The priesthood would be open to all men.
Mormonism has extra appeal for some Latin Americans because its doctrine gives special status to those who inhabited the Americas before the European conquest. The Book of Mormon teaches that a group of Israelites sailed to the New World thousands of years before Columbus, and their descendants were the original Mormons.
Today, the Mormon temple in a working class section of Mexico City is decorated with stylized designs inspired by the Mayan people. "Members of the Church value the people of Mexico and Central and South America," said one member of the faith, Nancy Ramirez, in an interview at the temple.
Ties date back to the late 1800s when Mormon families moved to Mexico on missions and to escape prosecution for polygamy, which was illegal in the United States. Mitt Romney's great-grandfather helped set up Mormon Mexican colonies, some of which still exist in northern Mexico. Some Romneys still live there, though they stopped practicing polygamy decades ago.
(See: FEATURE-Romney's Mormon ancestors built haven in Mexican desert - link.reuters.com/zan76s )
George Romney, Mitt Romney's father, was born in a Mormon colony in Mexico, though the immediate family fled back to the United States in 1912, driven out during the Mexican revolution.
Latin America now accounts for 40 percent of the church's more than 14 million global members, and Hispanics are a small but fast-growing part of U.S. membership as well.
Demographers at The Cumorah Project, a private research effort by Mormons which is not affiliated with the Church, say Latin Americans will probably outnumber U.S.-based Mormons within a couple of decades - although they caution that church numbers do not reflect sizeable defections. Mexicans who identified themselves as Mormons on the Mexican national census were a quarter of the church figure, for instance.
Mesa resident Pablo Felix was 17 when friends sent Spanish-speaking missionaries to his house. His entire Catholic family converted, following his mother's lead.
Felix, now 41, says the Mormon scriptures can have a powerful impact on Hispanics. "They say, 'this book is about me.' That's what I told my kids - this book is about us, years ago, thousands of years ago. And you know what? It's a beautiful thing," Felix said.
It was Pearce's introduction of the Arizona immigration bill, which called on state and local police to routinely check immigration status and pursue deportation aggressively, that forced immigration onto the Mormon community's agenda.
In Mesa, where the Spanish-speaking Liahona ward has grown and split into at least six different congregations, "there was a backlash," said Felix. He eventually became a ward leader and estimated that at the time 70 percent to 80 percent of its congregants were illegal immigrants.
"People would ask me if I supported Russell Pearce," said Uvaldo, one illegal immigrant who has been in the United States since 1995. Uvaldo, who asked that his full name not be printed, said he answered that people in his religion had a range of views.
The church has stepped quietly but firmly into the national immigration debate, bucking its reputation for social conservatism by casting immigration as a moral issue rather than one of law and order. It does not endorse candidates, but it does take positions on moral issues in politics.
In Arizona, voters recalled Pearce last November, and the church rebuffed him shortly before the vote, denying that it backed an "enforcement only" approach.
"The church's position on immigration is affected by the fact that it's a worldwide church," said Daryl Williams, a Republican lawyer in the Phoenix area who was one of the most prominent Mormon voices against the Arizona immigration law.
Voters replaced Pearce with Jerry Lewis, another Republican Mormon with a more moderate position on immigration. Pearce declined to be interviewed for this story.
In Utah, the church carefully maneuvered to block a movement towards an Arizona-style immigration law.
Though generally shy about direct political involvement - especially in light of the controversy generated by its overt opposition to same-sex marriage in California in 2008 - the church made several public statements urging compassion for families and its members worked the halls of the state Capitol, Utah politicians say.
The church has said it does not tell politicians how to vote, and Romney has emphasized that he makes his own decisions.
Paul Mero, a Mormon and the head of the conservative Sutherland Institute, was part of the group that came together to stop Utah from passing an Arizona-style law. He supports Romney and writes off the candidate's hard talk on immigration as election-year politics.
"He's talking to delegates. When he gets into office who knows what the policy's really going to be," Mero said.
Nora Castaneda in Mesa, though, is not convinced. She expects she'll eventually be voting for President Barack Obama, which is not surprising, since she is a Democrat. But she says her husband, a Latino Mormon Republican, feels the same way.
Additional reporting by Mica Rosenberg in Mexico City and Malathi Nayak in San Francisco; Editing By Jonathan Weber, Claudia Parsons