BELMONT, Mass. » When Mitt Romney embarked on his first political race in 1994, he also slipped into a humble new role in the Mormon congregation he once led. On Sunday mornings, he stood in the sunlit chapel here teaching Bible classes for adults.

Leading students through stories about Jesus and the Nephite and Lamanite tribes who Mormons believe once populated the Americas and tossing out peanut butter cups as rewards, Romney always returned to the same question: How could students apply the lessons of Mormon scripture in their daily lives?

Now, as the presumptive Republican nominee for president, Romney speaks so sparingly about his faith — he and his aides frequently stipulate that he does not impose his beliefs on others — that its influence on him can be difficult to detect.

But dozens of the candidate’s friends, fellow church members and relatives describe a man whose faith is his design for living. The church is by no means his only influence, and its impact cannot be fully untangled from that of his family, which is also steeped in Mormonism.

But being a Latter-day Saint is "at the center of who he really is, if you scrape everything else off," said Randy Sorensen, who worshipped with Romney in church.

As a young consultant who arrived at the office before anyone else, Romney was being "deseret," a term from the Book of Mormon meaning industrious as a honeybee, and he recruited colleagues and clients with the zeal of the missionary he once was. Mitt and Ann Romney’s marriage is strong because they believe they will live together in an eternal afterlife, relatives and friends say, which motivates them to iron out conflicts.

Romney’s penchant for rules mirrors that of his church, where he once excommunicated adulterers and sometimes discouraged mothers from working outside the home. He may have many reasons for abhorring debt, wanting to limit federal power, promoting self-reliance and stressing the unique destiny of the United States, but those are all traditionally Mormon traits as well.

Outside the spotlight, Romney can be demonstrative about his faith: belting out hymns ("What a Friend We Have in Jesus") while horseback riding, fasting on designated days and finding a Mormon congregation to slip into on Sundays, no matter where he is.

Clayton M. Christensen, a business professor at Harvard and a friend from church, said the question that drove the Sunday school classes — how to apply Mormon gospel in the wider world — also drives Romney’s life. "He just needs to know what God wants him to do and how he can get it done," Christensen said.

A MAN OF RULES

Romney is quick to uphold rules great and small. During primary debates, when his rivals spoke out of turn or exceeded their allotted time, he would sometimes lecture them. When supporters ask Romney to sign dollar bills or U.S. flags, he refuses and often gives them a little lesson about why doing so is against the law.

Doing things by the book has been a hallmark of his career in public life. When Romney took over the Salt Lake City Olympics, which were dogged by ethical problems, he cast himself as a heroic reformer. As governor of Massachusetts, he depicted himself as a voice of integrity amid what he called the back-scratchers and ethically dubious lifers of state government.

In church, Romney frequently spoke about obeying authority, the danger of rationalizing misbehavior and God’s fixed standards. "Most people, if they don’t want to do what God wants them to do, they move what God wants them to do about four feet over," he once told his congregation, holding out his arms to indicate the distance, Christensen remembered.

Church officials say Romney tried to be sensitive and merciful; when a college student faced serious penalties for having premarital sex, Romney put him on a kind of religious probation instead. But he carried out excommunications faithfully. "Mitt was very much by the rules," said Tony Kimball, who later served as his executive secretary in the church.

But many also see a gap between his religious ideals and his political tactics. The chasm has been hard to reconcile, even though people close to him say he is serious about trying to do so.

For example, Romney had ruled out running personal attack ads against political rivals, those close to him said. When Sen. Edward M. Kennedy attacked him as an uncaring capitalist in 1994, using ads that exaggerated Romney’s role in Bain-related layoffs, Romney refused to punch back and exploit Kennedy’s history of womanizing. "Winning is not important enough to put aside my ideals and principles," Romney told aides.

Last week, Romney repudiated efforts to attack Obama based on his past relationship with the Rev. Jeremiah A. Wright Jr. But earlier this year, he suggested that Obama wanted to make the United States "a less Christian nation."

"I have absolutely no idea how he rationalizes it," Kimball said of Romney’s harshest statements and attacks. "It almost seems to be the ends justifying the means."

RELYING ON PRAYER

Though Romney almost never discusses it or performs it in public, prayer is a regular and important part of his life, say friends who have joined him. "Prayer is not a rote thing with him," said Ann N. Madsen, a Bible scholar and a friend. Rather than requesting a specific outcome, he more often asks for strength, wisdom and courage, according to several people who have prayed with him. "Help us see how to navigate this particular problem," he often asks, according to Dr. Lewis Hassell, who served with Romney in church.

Romney has also asked for divine sustenance during his political runs. The night before he declared his candidacy for governor, he and his family prayed at home with Gloria White-Hammond and Ray Hammond, friends and pastors of a Boston-area African Methodist Episcopal church.

His earlier failed run for U.S. Senate had all been part of God’s plan, Ann Romney told Gloria White-Hammond around that time. Mitt Romney had lost, but "just because God says for you to do something doesn’t mean the outcome is going to be what you want it to be," White-Hammond remembered Ann Romney saying.

About a year ago, Ann Romney told White-Hammond that her husband was probably going to run for president again, and that they were both already praying about the race.

Mitt Romney was still a bit reluctant to re-enter the fray, according to White-Hammond. But she recalled the soon-to-be candidate’s wife saying that the Romneys both "felt it was what God wanted them to do."