Under what 2 circumstances did Lyndon B. Johnson become the US President?
Lyndon B. Johnson became president of the United States after the assassination of John F. Kennedy in November 1963 thus paving way for him to serve as the president from 1963-1969.
The invitation by John F. Kennedy in 1960, the Democratic presidential nominee, requesting Johnson to be his vice-presidential running mate. Johnson’s presence on the ticket attracted the support of conservative Southern Democrats and helped lift Kennedy to a narrow victory over Republican candidate Richard M. Nixon. Thus after John F. Kennedy's assassination, Johnson ascended to power becoming the 36th president of the United States of America.