Vice President Joseph R. Biden Jr., who is president of the Senate, and three top officers of the chamber have been named in a lawsuit trying to overturn the Senate's filibuster rule. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

Vice President Joseph R. Biden Jr., who is president of the Senate, and three top officers of the chamber have been named in a lawsuit trying to overturn the Senate's filibuster rule. (AP Photo/Charles Dharapak)