Even before today's hearing at the Supreme Court, an unofficial lobbying effort has been underway on Capitol Hill. As Politico's Ben Schreckinger reports, the children of prominent Republican politicians say they've seen their own parents struggle with and evolve in their views of marriage equality.
And in some cases, that evolution has come about through personal pleas.
Matt R. Salmon is the son of Arizona Rep. Matt Salmon, who voted for a ban on gay adoption and for the Defense of Marriage Act. His mother, Nancy, led a failed 2006 campaign to amend Arizona's constitution to ban not only same-sex marriage, but legal recognition of any kind for same-sex couples.
So it's no surprise that Matt's parents, among the staunchest opponents of same-sex marriage, enrolled him in "reparative therapy" to reverse the homosexuality that he said made him and his parents feel ashamed.
But in 2008, Matt walked away from that controversial practice and embraced his sexual identity. He came out to friends, and changed his status on Facebook to gay.
His parents, he said, have come to embrace it, too. "If you want to know the truth, my father was the first to come around," said Matt.
"He's been exposed to a lot more in his life, especially given his position. He's been exposed to a lot more ideas that are different than his own."
That's not reflected in his Congressional Record, however. In 2013, Matt's father -- who served in the House from 1995-2001 and returned to the chamber that year -- said that despite his son's identity, he continued to oppose marriage equality.
But that's not the full story, according to Matt. Late in 2013, as the two drove to a motorcycle expo in Scottsdale and chatted about the media frenzy over the congressman's comments, Salmon confided that he would happily attend his son's wedding, whenever that may be.
Since then, said Matt, his mother and father have come around to fully accept his sexual identity. "They've all only evolved more, to the point where they want to know about my dating life, where they want to know if anybody's in my life making me happy."
Even Matt's boyfriends have been "welcomed with open arms" at family events, and his mother has vowed to never again involve herself in anti-same-sex marriage campaigns. Matt said that Salmon's fellow conservative congressmen have approached his dad to thank him, crediting his relationship with Matt as having helped them evolve their thinking on LGBT issues.
Politico reports Matt said he'd love to go into the details of the conversations he's had with his father on those issues, but that he can't.
"There are opinions that my father privately holds that are different from his political positions that make them difficult to share," said Matt.
He said of his father: "Privately, things have evolved," but that's where the buck stops. "As far as I know, his political stances haven't changed."
"It's a private matter between him and his son," said a spokesman for the congressman.
Sen. Jeff Flake of Arizona was considering a vote for the Employment Non-Discrimination Act in 2013, which would protect gay and transgender people, when he posed a question to his son Ryan as the two sat in his Washington office.
"Do you think homosexuality is a choice?" Flake asked, according to Ryan.
Ryan, whose best friend and cousin had just come out, sending "shockwaves" through their conservative Mormon family, told his dad no, not usually.
"He just sat there and pondered it for a while," Ryan said. "That got to me. He was really trying to gather opinions."
Later that year, Democrat Tammy Baldwin, the nation's first openly gay senator, approached Flake to lobby his support for the bill. She asked Flake to speak with a conservative Republican lawmaker with a transgender child (that child is still a minor, and Ryan declined to share the lawmaker's name).
That conversation, Flake's office confirmed, helped seal what The Advocate called his "surprise" vote in favor of the bill.
Since then, Ryan has become an increasingly avid advocate for gays and lesbians. Earlier this month, he marched in the Phoenix Pride parade. He's joined pro-same-sex marriage Mormon groups and started volunteering at a shelter for LGBT youth.
Ryan told his father that he thinks the young people he works with should be able to get married one day - and he describes his dad as a good listener.
"I'm not saying he supports marriage equality. I can't say that. I just can't comment on that," said Ryan. "I do think his views have evolved. He's in a place in Washington, D.C., where he's had to deal with different people."
He added, "Just as any other politician has to, there has to be a difference between private belief and what the majority may want."
When asked about his current position on same-sex marriage, Jeff Flake said, through a spokeswoman, "This issue is now in the hands of the courts."
Politico reports the other "surprise" vote in favor of ENDA in November 2013 was Flake's Arizona colleague, Sen. John McCain. His daughter Meghan, a pundit and LGBT rights activist who will co-host a country music concert being put on by GLAAD in June, said she's discussed LGBT issues with her father, though he continues to oppose same-sex marriage both publicly and privately.
"There's tension when I go home on occasion but my father and I get along great," said Meghan McCain. "Obviously, I wish he would come around publicly for LGBT rights and marriage equality, but he's 80 years old."
As acceptance of same-sex marriage becomes more mainstream in the Republican Party, its aging leaders face a similar dilemma. Polls show 61 percent of Republicans ages 18-29 favor same-sex marriage, compared to 22 percent of those age 65 and up.
Within prominent Republican families, that divide means children - gay, transgender, and straight -- are playing decisive roles in changing their parents' views, and may help turn the tide at the High Court.
Florida Rep. Ileana Ros-Lehtinen was one of 300 Republicans to sign on to an amicus brief in support of same-sex marriage filed last month with the Supreme Court. She's said her transgender son Rodrigo Heng-Lehtinen, who was born as a girl and came out to her parents as lesbian before identifying as a man, has influenced her views on gender and sexuality.
"One of the biggest ways that my sister and I influenced my mother's views on LGBT issues was by simply speaking about them openly," said Heng-Lehtinen. "Growing up, my sister Patty and I did not hide our LGBT friends nor shy away from discussing LGBT topics in the news. This was the case long before I came out as a transgender man."
In March 2013, Sen. Rob Portman of Ohio became the first Republican senator to announce his support for same-sex marriage, two years after his son Will came out to his parents as gay.
Last summer, a lesbian relative of the wife of potential presidential contender Scott Walker married another woman, and Walker's son Alex acted as a witness. The Wisconsin governor has said that both of his sons have pushed the view that government should have no hand in regulating marriage. "That's a solid argument," Walker told Buzzfeed in 2013. "I personally may not embrace that yet. But that, to me, is a bigger question... I get their concerns."
Earlier this month, Arkansas Gov. Asa Hutchinson refused to sign a "religious freedom" bill that critics said would have permitted discrimination against gays, citing the influence of his son Seth, a liberal labor organizer in Texas, who emailed his father about his objections to the bill. "
I didn't really come up with any original arguments on it," said Seth Hutchinson - a sign that the messenger often matters as much as the message.
This report is based on and includes writing by Ben Schreckinger of politico.com