Lyndon Johnson gave several reasons for his decision not to run for re-election. Among them were his desire to spend more time with his family and the fear that he would not live until the end of his term if re-elected. Though the reasons behind Johnson's decision not to seek re-election have been often debated, his appointment secretary -- a position similar to today's chief of staff -- firmly believes there was only one reason Johnson chose to step down: Vietnam.

Assassination of Kennedy

Johnson's first term in office was not by election. In 1960, Johnson was the vice-presidential running mate of John F. Kennedy, a charismatic statesman and the first Roman Catholic to run for president. Kennedy hoped that Johnson, a Texas native, would attract the support of southern Democrats. Kennedy and Johnson proved to be a winning combination, defeating Republican Richard M. Nixon by a slim margin. On Nov. 22, 1963, Kennedy was assassinated. Hours later, Johnson was sworn in the as the new president.

Election of 1964

Johnson proved his popularity among voters with a decisive win over Barry Goldwater in the 1964 presidential election. Johnson had already pushed through most of Kennedy's domestic policies, laying the groundwork for his own Great Society, as Johnson called his vision for America. He signed the Civil Rights Act of 1964 and the Voting Rights Act of 1965. He launched his War on Poverty with the Medicare and Medicaid programs, providing health insurance for the poor and elderly. Unfortunately, Johnson also inherited the Vietnam conflict from Kennedy, a conflict that troubled him deeply.

The Vietnam Problem

Johnson was, at least in the beginning of his presidency, both morally and politically committed to the Vietnam War. He believed North Vietnam's conquest of South Vietnam would lead to the spread of communism throughout Asia. Johnson's solution was to escalate the war quickly in hopes that swift, concentrated pressure was key to defeating North Vietnam. Johnson increased the commitment of troops to 500,000 by 1968. Unfortunately, he underestimated North Vietnam's will to win. His escalation of the war only led to more casualties.

Decision Not to Run

According to James R. Jones, Johnson's former chief of staff, Johnson first discussed not running for re-election in late 1967 and planned announcing the decision during his state of the union address in January 1968. Johnson changed his mind, later telling Jones he wanted to complete additional legislation before becoming a lame-duck President. Jones said Johnson's decision not to announce led him to conclude Johnson just couldn't give up his Presidential powers.

A Personal Tragedy

Johnson told Jones his decision not to run again was partly based on his desire to spend more time with his grandchildren. Johnson also worried he would die in office if re-elected. Jones disputes theories that Johnson was afraid he would lose the 1968 election, pointing to results of a survey taken early in 1968 showing Johnson was more popular than all the announced candidates. According to Jones, Johnson's belief he would not be able to honorably conclude the Vietnam war was his primary reason for not seeking re-election. Richard N. Goodwin, special assistant to Johnson from 1964 to 1965, has said the Vietnam War was a tragedy for the U.S. and a "personal tragedy" for Johnson.