Public opinion on gay marriage has shifted faster in recent years than almost any other topic. Behind the change of heart has been a re-examination that is both institutional and personal.
Paul Anderson in the central California city of Bakersfield in 2008 voted for Proposition 8, the state gay-marriage ban that could be the subject of a Supreme Court decision this week. Mr. Anderson and his wife had heard from leaders in their Mormon church that the ban would protect families. They staked a pro-Prop 8 sign on their lawn.
But the controversy that emerged over Prop 8 was a catalyst for the 42-year-old financial planner to rethink his position. He began to question the view he heard in his church community about the agendas of gay people. "It bothered me enough that I thought, 'I have to figure this out for myself.' " He says: "It's the one vote I wish I could take back."
In the five years since Prop 8 passed, attitudes across America on gay marriage have moved fast. A poll this year by the nonpartisan Pew Forum on Religion and Public life found that 50% of Americans support gay marriage, up from 39% in 2008. "For a social issue in recent decades, that is quite unique," says David Masci, a senior researcher at the Pew Forum.
Even among religious and demographic groups largely opposed to gay marriage, more people support the idea today than five years ago. Among white evangelical Protestants, for example, support for gay marriage has grown from 16% to 23% since 2008, Pew found.
When Prop 8 passed in 2008 with 52% of the vote, only two other states permitted gay marriage. Today, 12 states plus the District of Columbia do so. U.S. voters had always chosen at the ballot to ban gay marriage until last fall, when they approved measures in Maine, Maryland and Washington.
Pinpointing reasons for the shift is difficult, but some point to Prop 8 itself as a catalyst. Reaction to the ban in the largest state has dominated headlines, generated difficult conversations and prompted gay-rights advocates to expand their outreach to minority groups and churches.
One turning point came in May 2012, when President Barack Obama said he felt gay people should be able to get married. The National Association for the Advancement of Colored People swiftly followed with its own resolution supporting gay marriage. A month later, the National Council of La Raza, the Latino civil-rights group, did the same. Both groups had stayed on the sidelines during the original Prop 8 fight.
"We were very aware that if we did this the right way at the right time, we could bring with us the entire force of the organization on the issue," says Benjamin Jealous, president of the NAACP. The group's California chapter actively campaigned against Prop 8 back in 2008 though the national organization didn't.
Support hasn't been universal. Trina Williams, a 53-year-old gay-marriage opponent in Inglewood, Calif., told the president of her local NAACP chapter recently that she won't support the organization any longer because of the national endorsement of gay marriage. As she leaves the organization, she plans to redouble her efforts to keep gay people from getting married.
God created marriage "for one man and one woman and for procreation reasons," Ms. Williams says. "I believe if I'm part of an organization, I should share their opinions—and I just don't."
Some churches that remained silent in 2008 have also taken a dramatic turn. As early as 2009, the Evangelical Lutheran Church in America said pastors could bless same-sex unions, leaving room for some pastors to conduct gay marriages for the first time.
In July 2012, the Episcopal Church approved a service for blessing same-sex relationships.
At St. John's Episcopal Church in Roseville, Calif. many worshippers opposed gay marriage and those who disagreed kept their beliefs private when Prop 8 was on the ballot, says rector Rev. Clifford Haggenjos. But increasingly, congregants became more open.
In 2011, Mr. Haggenjos blessed a gay couple celebrating their anniversary and some in the congregation burst into applause. Still, while Mr. Haggenjos had voted against Prop 8, he didn't feel comfortable marrying gay couples.
When the church published materials explaining its new positions in 2012, he says, the church's position "really moved me into a position where I was open to performing same-sex blessings."
Amidst the national conversation, gay-rights advocates say more gay and lesbian Americans are coming out of the closet, making the issue more personal to straight voters.
In Mr. Anderson's Bakersfield Mormon community, Wendy and Tom Montgomery hadn't given a second thought to supporting Prop. 8. In 2008, they volunteered to canvass for votes door to door and on the phone.
Ms. Montgomery, 37, did an about face last year after her son Jordan told her he was gay.
"All of a sudden, I had this 13-year-old boy who is gay, and none of those stereotypes or preconceived judgments fit," Ms. Montgomery said.
The family has since become vocal advocates for gay rights and starred in a short film called "Families Are Forever" to help those struggling with coming out.
The Church of Jesus Christ of Latter-day Saints still officially opposes gay marriage, and filed a brief to the Supreme Court in support of Prop 8.
Ms. Montgomery and her family still go to church—and want marriage to a man to be an option for Jordan. "At church, the highest form of happiness is being married and having a family. I am not going to tell him that all those things are available to everybody except him," Ms. Montgomery says.