NYT:

Dozens of prominent Republicans—including top advisers to former President George W. Bush, four former governors and two members of Congress—have signed a legal brief arguing that gay people have a constitutional right to marry, a position that amounts to a direct challenge to Speaker John A. Boehner and reflects the civil war in the party since the November election. The document will be submitted this week to the Supreme Court in support of a suit seeking to strike down Proposition 8, a California ballot initiative barring same-sex marriage, and all similar bans. The court will hear back-to-back arguments next month in that case and another pivotal gay rights case that challenges the 1996 federal Defense of Marriage Act.

The Proposition 8 case already has a powerful conservative supporter: Theodore B. Olson, the former solicitor general under Mr. Bush and one of the suit’s two lead lawyers. The amicus, or friend-of-the-court, brief is being filed with Mr. Olson’s blessing. It argues, as he does, that same-sex marriage promotes family values by allowing children of gay couples to grow up in two-parent homes, and that it advances conservative values of “limited government and maximizing individual freedom.”

Legal analysts said the brief had the potential to sway conservative justices as much for the prominent names attached to it as for its legal arguments. The list of signers includes a string of Republican officials and influential thinkers —75 as of Monday evening—who are not ordinarily associated with gay rights advocacy, including some who are speaking out for the first time and others who have changed their previous positions.

Among the signers of the amici brief are Ken Mehlman, Steve Schmidt, Meg Whitman, Jon Huntsman, "Stephen J. Hadley, a Bush national security adviser; Carlos Gutierrez, a commerce secretary to Mr. Bush; James B. Comey, a top Bush Justice Department official; David A. Stockman, President Ronald Reagan’s first budget director; and Deborah Pryce, a former member of the House Republican leadership." The brief directly addresses—and demolishes—the arguments put forward by opponents of same-sex marriage:

Deinstitutionalization. No credible evidence supports the deinstitutionalization theory.... Petitioners fail to explain how extending civil marriage to same-sex couples will dilute or undermine the benefits of that institution for opposite-sex couples... or for society at large. It will instead do the opposite. Extending civil marriage to same-sex couples is a clear endorsement of the multiple benefits of marriage—stability, lifetime commitment, financial support during crisis and old age, etc.—and a reaffirmation of the social value of this institution.

Biology. There is also no biological justification for denying civil marriage to same-sex couples. Allowing same-sex couples to marry in no way undermines the importance of marriage for opposite-sex couples who enter into marriage to provide a stable family structure for their children.

Child Welfare. If there were persuasive evidence that same-sex marriage was detrimental to children, amici would give that evidence great weight. But there is not. Social scientists have resoundingly rejected the claim that children fare better when raised by opposite-sex parents than they would with same-sex parents.