Final answer:
Antiwar protests, and the internal division within the Democratic Party, significantly influenced President Johnson's decision not to seek reelection in 1968. The public's growing disapproval of the Vietnam War and high-profile criticism played a crucial role in shaping political outcomes, demonstrating the power of popular opinion and opposition on the national stage.
Step-by-step explanation:
Antiwar protesters discouraged President Johnson from seeking reelection, showing that strong public dissent and a divided Democratic Party could heavily influence political decisions. By 1967, protests grew, with tens of thousands of attendees, and the opposition's voice became stronger. The Vietnam War, coupled with the growing unpopularity of the Johnson administration's policies, led many to doubt the government's strategy, especially after the impactful Tet Offensive and the public commentary by Walter Cronkite, who expressed skepticism about the war's winnability.
President Johnson's commitment to Vietnam's slow escalation was not enough to maintain his support. Minnesota senator Eugene McCarthy's near-success in New Hampshire and Robert Kennedy's entry into the race signified party dissonance. This internal conflict, alongside Johnson's health issues and public dissatisfaction, culminated in his decision not to seek reelection, announced on March 31, 1968.
Ultimately, Johnson's choice not to run reflected the inevitable consequence of low approval ratings and dissent within his own party alongside the broader antiwar sentiment prevalent among the American public and even within the military, evidenced by occurrences like 'fraggings'. The withdrawal from the race also came as a response to the broader context of an America deeply divided over the war, which had been significantly trailblazed by the doves and Vietnam Veterans Against the War who questioned America's involvement in Vietnam.