Same-sex marriage emerged as an issue in the late 1980s, drawing opposition especially from socially conservative groups. Congressman Bob Barr and Senator Don Nickles, both members of the Republican Party, introduced the bill that became DOMA in May 1996. It passed both houses of Congress by large, veto-proof majorities, with opposition coming from approximately one-third of the Democratic caucus in both the House of Representatives and the Senate. Clinton criticized the law as "divisive and unnecessary," but nonetheless signed it into law in September 1996.