He was the co-founder and first secretary-general of the People's Action Party (PAP), and led the party to a landslide electoral victory in 1959. During his leadership, Lee campaigned for a merger with other former British territories in a national referendum to form the Federation of Malaysia in 1963. However, racial issues and ideological differences led to Singapore's being forced to leave from the federation, and it became its own country on 9 August 1965.