Final answer:
President Lyndon Johnson, amidst growing unpopularity of the Vietnam War, announced that the U.S. would negotiate to end the war and that he would not run for reelection in 1968. His decision influenced the shift towards negotiations with North Vietnam and set in motion the gradual withdrawal of U.S. troops under his successor, President Nixon.
Step-by-step explanation:
President Lyndon Johnson's Decision During the Vietnam War
In the context of the Vietnam War's unpopularity, President Lyndon Johnson took several significant actions. Facing intense criticism over the war and suffering from health issues, Johnson realized that his public standing was greatly hurt by the war. In a turning point of the American political landscape, on March 31, 1968, Johnson made a groundbreaking announcement. He declared that the U.S. would begin negotiations to end the war in Vietnam and significantly, that he would not seek nor accept the nomination for presidency in the upcoming election, effectively choosing not to run for reelection. This decision was a response to the deep divisions within the Democratic Party and the nation's growing anti-war sentiment. Johnson's announcement paved the way for the eventual withdrawal of U.S. forces from Vietnam, although this process would be carried out under President Nixon, who succeeded Johnson after winning the closely contested 1968 election.