Dale L. Bumpers, a liberal governor and four-term Democratic senator from Arkansas who came out of retirement in 1999 to make a passionate closing argument defending President Bill Clinton against removal from office in a Senate trial, died on Friday at his home in Little Rock, Ark. He was 90. His death was confirmed by his granddaughter Linn Bumpers. Mr. Bumpers was part of a generation of moderate Southern Democrats, among them President Jimmy Carter, who emerged in the late 1960s and the ’70s. He always said his proudest achievement had come early in his career when, as a small-town...