As polls show larger and larger majorities of Americans favoring gay marriage, the opponents recognize they might be losing the battle of public opinion.

"Are we bucking the tide when it comes to cultural elites?" Brown says, before answering his own question. "Of course. We know that."

Cordileone: 'A Bitterly Polarized Country'

No group opposing gay marriage carries as much influence as the Catholic bishops, and Cordileone is their point man. He's a baby boomer from Southern California who takes the assignment seriously.

To Cordileone, 56, the effort combines a respect for ancient civilizations as well as an understanding of modern families. He's aware many of his flock disagree with the church's teachings on the issue, particularly in San Francisco, but he sees no conflict.

"My job as an archbishop is to teach the truths of our faith and the truths of the natural moral law, and whatever challenges that entails, I embrace with enthusiasm," he said.

The modern-day version of that history lesson, Cordileone said, could be seen from his cathedral residence overlooking Lake Merritt when he served as bishop of Oakland.

"It's very beautiful," he recalls. "But across the lake, as the streets go from 1st Avenue to the city limits at 100th Avenue, those 100 blocks consist entirely of inner-city neighborhoods plagued by fatherlessness and all the suffering it produces: youth violence, poverty, drugs, crime, gangs, school dropout and incredibly high murder rates.

"Walk those blocks and you can see with your own eyes: a society that is careless about getting fathers and mothers together to raise their children in one loving family is causing enormous heartache."

Ask this San Diego native if he has gay friends and the answer is, "Of course!" His views on gay marriage don't cause heartache in those relationships, he said, because his friends know him.

"It's a lot harder to be hateful or prejudiced against a person, or group of people, that one knows personally," he said. "When there is personal knowledge and human interaction, the barriers of prejudice and preconceived ideas come down."

Regardless of what rulings the Supreme Court hands down this summer, Cordileone warns that the debate is not over.

"Just as Roe v. Wade did not end the conversation about abortion, so a ruling that tries to import same-sex marriage into our Constitution is not going to end the marriage debate, but intensify it," he said. "We will have a bitterly polarized country divided on the marriage issue for years if not generations to come."

Diaz: 'This is What I Preach'

In some respects, Owens and Diaz defy the common perception that African-Americans and Hispanics are overwhelmingly liberal. It's a perception these men dispute.

The 74-year-old Owens, president of the Coalition of African-American Pastors, a co-sponsor of Tuesday's march, contends blacks always have been "conservative Christians."

"I go from a biblical standpoint and a social standpoint, knowing the damage that has already been done to the black family," he said. The threat of same-sex marriage, he added, represents "another nail in the coffin for black families."

Once divorced himself, Owens acknowledges that legalizing gay marriage won't directly affect him. Still, he says, "We just don't know where it's going."

Diaz, an ordained minister in the Church of God who chairs the New York Hispanic Clergy Organization, is bringing 25 to 30 buses with gay marriage opponents to Washington for Tuesday's rally. Four years ago, he assembled a crowd of 20,000 to protest New York's burgeoning gay marriage movement.

"The Hispanic community is more conservative than what people think," he says. "Call it whatever you want -- it's a conservative religious movement."