Nixon campaigned on a theme to restore "law and order," which appealed to many voters angry with the hundreds of violent riots that had taken place across the country in the previous few years. Following the murder of Martin Luther King in April 1968, there was massive rioting in inner city areas. The police was [sic] overwhelmed and President Johnson had to call out the U.S. Army.
Source: Wikipedia, "1968 United States Presidential Election."
