"So I will add my name to the petition of senators asking the Supreme Court to declare the law that prohibits gay marriage unconstitutional," Nelson said.
Nelson's announcement cuts down the number of Senate Democrats who do not support same-sex marriage to six. The remaining Democrats are Sens. Joe Manchin (W.Va.), Joe Donnelly (Ind.), Tim Johnson (S.D.), Heidi Heitkamp (N.D.), Mary Landrieu (La.) and Mark Pryor (Ark.).
The lawmakers who recently reversed their position and now support same-sex marriage are Democratic Sens. Jay Rockefeller (W.Va.), Mark Warner (Va.), Bob Casey (Pa.), Kay Hagan (N.C.), Claire McCaskill (Mo.), Mark Begich (Alaska), Jon Tester (Mont.) and Tom Carper (Del.). Besides Kirk, Sen. Rob Portman (R-Ohio) supports same-sex marriage. Portman made the announcement in March.