Which of the following events led to a sharp decline in President Johnson's popularity? A) the Korean War B) the Vietnam War C) the Watergate Scandal D) the Bay of Pigs Invasion

The correct answer is B. The Vietnam War.

Johnson supported the Vietnam war effort which cost him a lot of the support. Korean war was led by Eisenhower while the Watergate Scandal involved Nixon. The bay of pigs invasion was done under Kennedy, which only leaves Johnson as the answer.