Republican White House challenger Mitt Romney, wooing social conservatives, adamantly rejected same-sex marriage Saturday and trumpeted his belief in Christian values and the family.
Three days after Barack Obama became the first US president to approve gay and lesbian marriage, Romney told university graduates that the "pre-eminence of the family" remains at the heart of the principles that underpin the nation.
"As fundamental as these principles are, they may become topics of democratic debate," the presumptive Republican nominee told the class of 2012 at Liberty University, the biggest Christian campus in the United States.
"So it is today with the enduring institution of marriage. Marriage is a relationship between one man and one woman," he said, raising a loud cheer from the 20,000-strong crowd -- the biggest so far in this campaign season.
Romney, who did not directly refer to gays or lesbians, previously voiced opposition to gay marriage, although he has also stated same-sex couples should have some rights such as child adoption.
But Saturday's speech, with which the Republican hopeful sought to set himself apart from Obama in the run up to November's election was his unbowed rebuttal in a week dominated by Obama's landmark endorsement of gay marriage.
"Central to America's rise to global leadership is our Judeo-Christian tradition, with its vision of the goodness and possibilities of every life," he said in a speech punctuated with references to God.
"Take those away, or take them for granted, and so many things can go wrong in a life. Keep them strong, and so many things will go right."
Romney, a former governor of Massachusetts and successful venture capitalist with a personal wealth estimated at more than $250 million, also tried to rebut his image as a corporate suit who puts profit before people.
"I have never once regretted missing a business opportunity so that I could be with my children and grandchildren," he said, while also referring to his wife Ann, a homemaker who is often by his side on the campaign trail.
"Among the things in life that can be put off, being there when it matters most isn't one of them," he said, while seeking to tap into a sense among many evangelicals and the Catholic church establishment that Obama is riding roughshod over the constitutionally guaranteed freedom of religion.
"It strikes me as odd that the free exercise of religious faith is sometimes treated as a problem, something America is stuck with instead of blessed with," Romney said.
"Perhaps religious conscience upsets the designs of those who feel that the highest wisdom and authority comes from government -- but from the beginning, this nation trusted in God, not man," he said.
"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."
Virginia is a key battleground in November's presidential election. First Lady Michelle Obama preempted Romney by delivering her own commencement speech at Virginia Tech university, about 90 miles (145 kilometers) from Lynchburg.
Romney was introduced to the stadium crowd -- 6,000 of whom were graduates -- by Liberty University president Jerry Falwell Jr, the son and namesake of its late Baptist founder, as "the next president of the United States."
Liberty, the largest evangelical university in the world, is something of an essential campaign stop for Republican presidential candidates, having previously hosted Ronald Reagan and the elder George Bush.
Its invitation to Romney stirred controversy among some evangelicals due to his Mormon background.
Last year pastor Robert Jeffress, a leader of the Southern Baptist Convention, the largest evangelical movement in the United States, dismissed Mormonism as "a theological cult."
Many core Republicans remain wary of Romney, with critics saying he is a moderate who has suspiciously shifted his stance on social issues like abortion.
A new poll by Religious News Survey shows that such doubts might be waning among some core conservatives, with Romney now enjoying a huge 68-19 percent lead over Obama among white evangelical voters.
The Democratic National Committee acknowledged a tough road ahead to convince evangelicals to vote for Obama, but insisted it was possible.
In a DNC-coordinated conference call, Liberty graduate student Christine Darby said it was Obama more than Romney whose policies "clearly reflect the justice and compassion that Christ preaches." AGENCIES