On March 31, 1968, then-incumbent U.S. president Lyndon B. Johnson made a surprise announcement during a televised address to the nation that began around 9 p.m.,[1] declaring that he would not seek re-election for another term and was withdrawing from the 1968 United States presidential election.

"[2][3] At first, Johnson's only significant challenger in the 1968 Democratic Party presidential primaries was Eugene McCarthy, an anti-war U.S. senator from Minnesota.

Johnson's decision and the assassination of Kennedy opened the door for Vice President Hubert Humphrey to become the Democratic Party's nominee.

Nixon's campaign capitalized on themes of law and order and a promise to end the Vietnam War conflict and United States involvement, which resonated with many voters.

The first group consisted of Johnson and Humphrey, labor unions, and local party bosses (led by Chicago Mayor Richard J. Daley).

His health was poor, and he was pre-occupied with the Kennedy campaign; his wife was pressing for his retirement, and his base of support continued to shrink.

[21] In 2009, an AP reporter said that Johnson decided to end his re-election bid after CBS News anchor Walter Cronkite, who was influential, turned against the president's policy in Vietnam.

They said that members of Johnson's inner circle, who had watched the editorial with the president, including presidential aide George Christian and journalist Bill Moyers, later confirmed the accuracy of the quote to them.

[26] However, Johnson's January 27, 1968, phone conversion with Chicago Mayor Richard J. Daley revealed that the two were trying to feed Robert Kennedy's ego so he would stay in the race, convincing him that the Democratic Party was undergoing a "revolution".

However, by withdrawing from the race, he could avoid the stigma of defeat, and he could keep control of the party machinery by giving the nomination to Humphrey, who had been a loyal vice-president.

Dallek concludes that Nixon's advice to Saigon made no difference, and that Humphrey was so closely identified with Johnson's unpopular policies that no last-minute deal with Hanoi could have affected the election.

"[37] After Johnson's withdrawal, many Republicans underwent an anguished reappraisal concerning Richard Nixon's chances for winning the election in November.

[39] During this time, South Vietnamese President Nguyễn Văn Thiệu was eagerly anticipating the results of the American election, believing he could secure a more favorable agreement with Republican candidate Nixon than with the incumbent administration.

President Johnson, enraged and appalled, discovered evidence of this through phone taps, intercepts, and surveillance, considering it a potentially treasonous act.

[40] Within the week of Johnson's announcement, American civil rights activist and oppositionist to the Vietnam War; Martin Luther King Jr., was assassinated in Memphis, Tennessee at the Lorraine Motel.

[43] After Johnson's withdrawal, and the assassination of Robert F. Kennedy, McCarthy was Humphrey's only major opponent until George McGovern entered the race.

Humphrey would end up losing the election to the antiwar Republican Richard Nixon, who portrayed himself as a figure of stability during this period of national unrest and upheaval.