“What you believe, what you value, how you live, matters,” Mr. Romney said. Mr. Romney’s speech was also notable for its overt religiosity, a tone that he had resisted, even during the Republican primaries, when conservative Christians were questioning his faith.

Mitt Romney traveled to Liberty University, the spiritual heart of the conservative movement, on Saturday, seeking to quell concerns about him among evangelical voters by offering a forceful defense of faith and Christian values in public life.

At a graduation speech at the college, founded by the evangelical leader Jerry Falwell, Mr. Romney made the case that he is bound theologically and politically to the same belief and value system as Christian conservatives, though he never explicitly mentioned his Mormon faith.

In the same week that President Obama galvanized his base by endorsing same-sex marriage, Mr. Romney’s message was that evangelicals could count on him to operate as president under “a common worldview,” including his position that marriage should be between only a man and a woman.

American values, he said, “may become topics of democratic debate from time to time. So it is today with the enduring institution of marriage. Marriage is a relationship between one man and one woman.”

It was Mr. Romney’s most extensive and direct discussion of religion since his 2007 speech about his own faith and was intended to help him reassure conservatives, some of whom do not accept Mormonism as a Christian religion.

Repeatedly invoking God and citing an array of Christian leaders and thinkers, from Pope John Paul II to the novelist C. S. Lewis, Mr. Romney spoke of the centrality of family and service and the tradition from America’s beginnings of trusting “in God, not man.”

“Religious liberty is the first freedom in our Constitution,” he said. “And whether the cause is justice for the persecuted, compassion for the needy and the sick, or mercy for the child waiting to be born, there is no greater force for good in the nation than Christian conscience in action.”

Mr. Romney acknowledged the divide between his church and evangelical Christians, while suggesting that they seemed more in sync than not.

“People of different faiths, like yours and mine, sometimes wonder where we can meet in common purpose, when there are so many differences in creed and theology,” Mr. Romney said. “Surely the answer is that we can meet in service, in shared moral convictions about our nation stemming from a common worldview.”

Mormons consider themselves Christians, as noted in the church’s formal name, the Church of Jesus Christ of Latter-day Saints, but evangelicals do not consider the Mormon scripture to be Christian.

Mr. Romney also alluded to abortion and the recent controversy of whether religious institutions should offer birth control in their health coverage, which is seen by evangelicals as an issue of religious freedom.

And in a nod to the Republican rival favored by many Christian conservatives, Mr. Romney mentioned Rick Santorum, saying that Mr. Santorum stressed that “culture matters,” that marriage, family and work determine success in life.

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