(Republican presidential candidate and former Massachusetts Governor Mitt Romney speaks during a campaign event in Mesa, Arizona February 13, 2012. REUTERS/Joshua Lott)

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.