(CNN) - Sen. Arlen Specter, the outgoing Pennsylvania Republican-turned-Democrat, directed a parting blow Tuesday to members of the Supreme Court's conservative bloc.
In his final speech on the Senate floor, Specter, the former GOP chairman of the Senate Judiciary Committee, chastised Chief Justice John Roberts and Justice Samuel Alito for "eroding the constitutional mandate of separation of powers."
"The Supreme Court has been eating Congress' lunch by invalidating legislation with judicial activism after nominees commit under oath in confirmation proceedings to respect congressional fact finding and precedents," said Specter, who voted in favor of both Roberts and Alito when the Bush appointees came before his panel.
Specter specifically took issue with the court's controversial 5-4 decision early this year, in which it relaxed federally-imposed campaign finance regulations for corporations and unions.
"Ignoring a massive congressional record and reversing recent decisions, Chief Justice Roberts and Justice Alito repudiated their confirmation testimony given under oath and provided the key votes to permit corporations and unions to secretly pay for political advertising - thus effectively undermining the basic Democratic principle of the power of one person, one vote," said Specter. Chief Justice Roberts promised to just call balls and strikes and then he moved the bases."
The divided decision last January in Citizens United v. Federal Election Commission eased long-standing restrictions on "independent spending" by corporations and unions, and radically altered the election calculus ahead of the midterm elections.
Specter, who left the Republican Party in 2009 in hopes of avoiding a difficult primary challenge, lost the Democratic primary earilier this year.
- CNN's Bill Mears and Virginia Nicolaides contributed to this report