Final answer:
President Lyndon B. Johnson announced he would not seek reelection due to the Vietnam War's unpopularity, health issues, and the division within the Democratic Party. He aimed to focus on ending the war without the complications of a reelection campaign.
Step-by-step explanation:
President Lyndon B. Johnson gave several reasons for not seeking reelection, which he announced in a televised address on March 31, 1968. Notably, the growing unpopularity of the Vietnam War had significantly eroded his standing with the public and within the Democratic Party. Moreover, the strong showings of senators Eugene McCarthy and Robert Kennedy, who both opposed the war, indicated that the party was divided. Additionally, Johnson was suffering from health problems and understood that his association with the Vietnam War had damaged his reputation. In an effort to prevent further division within the Democratic Party and to maintain a focus on ending the Vietnam War without the complications of a reelection campaign, Johnson made the decision to not seek another term.