The friend-of-the-court brief, expected to be filed this week, argues that same-sex marriage promotes family values by allowing children of same-sex couples to be raised in two-parent homes and advances conservative values of limited government and individual freedom, The New York Times reported.
The court will hear back-to-back arguments next month in a case seeking to strike down Proposition 8, the California ballot question barring same-sex marriage, and a challenge to the 1996 federal Defense of Marriage Act.
The list of signatories -- 75 as of Monday evening -- reads like a who's who of Republican officials and movers and shakers, including Meg Whitman, who supported Proposition 8 when she ran for California governor; Reps. Ileana Ros-Lehtinen of Florida and Richard Hanna of New York; Carlos Gutierrez, a commerce secretary to President George W. Bush; David A. Stockman, President Ronald Reagan's first budget director; and Deborah Pryce, a one-time member of the House GOP leadership now retired.
"Like a lot of the country, my views have evolved on this from the first day I set foot in Congress," Pryce told the Times. "I think it's just the right thing, and I think it's on solid legal footing, too."
Former Utah Gov. Jon Huntsman Jr., who favored civil unions but opposed same-sex marriage during his unsuccessful 2012 presidential bid, also signed the brief.
The brief, shared with the Times by its authors, cites Supreme Court rulings that conservatives cherish -- such as the Citizens United decision lifting campaign financing restrictions, and a Washington, D.C., Second Amendment case overturning a law barring handgun ownership, the newspaper said
"We are trying to say to the court that we are judicial and political conservatives, and it is consistent with our values and philosophy for you to overturn Proposition 8," said Ken Mehlman, a former Republican National Committee chairman who revealed his sexual orientation several years ago.
Mehlman is a board member of the American Foundation for Equal Rights, which brought the California suit, and has spent months talking to Republicans as he gathered signatures for the brief.
Gal Gadot cast as Wonder Woman for 'Batman vs. Superman'
Exploding whale video goes viral on Internet