In a real victory for supporters of same-sex marriage -- and marking what seems like real marginalization for its foes -- a major law firm has reversed course and will refuse to represent the House of Representatives in defending the Defense of Marriage Act.

King and Spalding Chairman Robert D. Hays, Jr., whose partner Paul Clement was to lead the defense, said in a statement through a spokesman, Les Zuke:

Today the firm filed a motion to withdraw from its engagement to represent the Bipartisan Legal Advisory Group of the House of Representatives on the constitutional issues regarding Section III of the 1996 Defense of Marriage Act. Last week we worked diligently through the process required for withdrawal.

In reviewing this assignment further, I determined that the process used for vetting this engagement was inadequate. Ultimately I am responsible for any mistakes that occurred and apologize for the challenges this may have created.

The statement is silent on the reasons for the decision, but the firm faced protests at its Atlanta office and a national campaign against it. And now the House majority may have to find a new lawyer.

UPDATE: Amanda Terkel reports that Clement has resigned from the firm. POLITICO's Josh Gerstein has more, including his resignation letter:

"I resign out of the firmly-held belief that a representation should not be abandoned because the client's legal position is extremely unpopular in certain quarters. Defending unpopular clients is what lawyers do ... I recognized from the outset that this statute implicates very sensitive issues that prompt strong views on both sides. But having undertaken the representation, I believe there is no honorable course for me but to complete it," writes Clement.