Debate over the war became fully politicized during the 1968 presidential election campaign. Sen. Eugene McCarthy (D-Minn.), running as an antiwar candidate, challenged incumbent President Johnson for the 1968 Democratic nomination and did surprisingly well in the New Hampshire primary. Newly appointed Secretary of Defense Clark Clifford became a key figure in persuading Johnson to halt the bombing and begin peace talks. On 31 March, after the meetings with his senior advisory group on Vietnam that led to the decision not to raise troop levels further, Johnson gave a televised talk to the nation, in which he announced a partial bombing halt, invited the North Vietnamese to begin negotiations, and announced — in a major surprise — that he would not run for reelection. Not long before Johnson's pullout, Sen. Robert Kennedy had entered the presidential race as an antiwar candidate. Vice-president Hubert Humphrey also sought the...