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 worshiped with Mr. Romney in church…

He prays for divine guidance on business decisions and political races, say those who have joined him. Sometimes on the campaign trail, Mr. and Mrs. Romney retreat to a quiet corner, bow their heads, clasp hands and share a brief prayer, said Representative Jason Chaffetz, a Utah Republican who has traveled with them.

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 Mr. Romney’s life. “He just needs to know what God wants him to do and how he can get it done,” Mr. Christensen said.