(WASHINGTON) -- The issue of same sex-marriage is dividing the Republican Party, as a group of more than 80 prominent members of the GOP, ranging from Dick Cheney's daughter to four former governors, have signed an amicus brief before the Supreme Court advocating for the legalization of gay marriage.
One of the signers confirmed for ABC News the existence of the brief signed by the Republicans and said it would be submitted to the United States Supreme Court this week. The deadline to submit briefs is Thursday.
The document, known as an amicus or "friend of the court" brief, is being submitted in support of a lawsuit aiming to strike down Proposition 8, the California ballot initiative that passed in 2008 banning same-sex marriage. The existence of the brief was first reported by The New York Times.
Republican-elected leadership, like House Speaker John Boehner, as well as the platform, are staunchly against same-sex marriage.
The American Foundation for Equal Rights (AFER), the group who brought the California lawsuit challenging Prop 8, released a list of the signers Tuesday, including Cheney's daughter Mary Cheney.
Signers included former congresswoman Mary Bono Mack of California, former presidential candidate Jon Huntsman, and Meg Whitman, who supported Prop 8 when she ran for governor of California in 2010. Representatives Ileana Ros-Lehtinen of Florida, Richard Hanna of New York and former GOP national chairman Ken Mehlman also signed. In addition, three former Massachusetts governors -- William Weld, Jane Swift, and Paul Cellucci -- along with former New Jersey governor Christine Todd Whitman are signers. The list also includes Republican attorney and Romney senior adviser Ben Ginsberg and other high-profile GOP leaders, strategists, consultants, and staffers.
Some big-name supporters of same-sex marriage who have not signed the brief include former Vice President Dick Cheney, former first lady Laura Bush, and former Secretary of State Colin Powell.
The fight against Prop 8 already had a big-name conservative supporter in Theodore Olson, former solicitor general under President George W. Bush, who is one of the suit's two lead attorneys along with David Boies.
The court will hear arguments next month in that case and another important gay rights case that challenges the 1996 federal Defense of Marriage Act.
Another one of the signers is Nicolle Wallace, Republican strategist and former George W. Bush aide and John McCain campaign adviser. Wallace said the beginning of the group took place in 2010 when Republicans supportive of same-sex marriage came together to fundraise for the legal effort.
She said the "power of the legal argument had a lot more to do with persuading the majority of Republicans on the brief than any political pressure."
Wallace stressed that she believes this issue, unlike others, will not "ignite a civil war in the party" because so many people have gay friends, co-workers, and family members; even those who don't agree with their stance have a lot of "respect" for the disagreement.
In the latest ABC News/Washington Post poll on the topic from November a slim majority of Americans support gay marriage, 51-47 percent, but amongst Republicans it is only 31-67 percent.
Brian Donahue, a Republican strategist who did not sign the brief, believes that because the list includes so many prominent Republicans it represents a "significant step" for the party.
"It's a sign that there is a growing interest in the party to take steps to broaden its reach in defining what's acceptable to be part of this party," Donahue said. "It's healthy for members of the party to express their beliefs and opinions even when they may not be favorable by party leadership. It's healthy for the party to examine how it affects the lives of all Americans and it's a healthy discussion that's taking place within the party to say, 'What do we stand for?'"
Some Republicans fear the amicus brief could badly split the Republican Party. Hogan Gidley, a GOP strategist who has worked on the presidential campaigns of both Mike Huckabee and Rick Santorum, says the Republican tent should be "very broad," but this move by the group of Republicans will widen the schism in the party.
"I don't want Republicans to be lazy and say, well Latinos are flocking to Democrats in droves so we should do amnesty," Gidley said. "The homosexual community is flocking to Democrats in droves so we should legalize gay marriage. The marijuana advocates are flocking to Democrats in droves, we should legalize drugs. To me that is a little bit reactionary, but also a little bit lazy."
Gidley said that he would "hate for anybody to sell their convictions in the hopes they get more votes."
Constitutional law experts say that while amicus briefs do not traditionally decide cases, they can be very influential.
Stanford constitutional law professor Jane Schacter says in this case she believes it could be an "influential brief" because it "telegraphs to the court that there is an increasing number of people who support same sex-marriage and that it is no longer a partisan issue to the extent that it was."
"When this number of Republicans are saying it's an issue where there should be equality it changes the way it looks to the justices," Schacter said.
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