It was founded in 1979 by left-wing leader Leonel Brizola as an attempt to reorganize the Brazilian leftist forces during the end of the Brazilian military dictatorship. Many of its members, including Brizola, had been active in the Brazilian Labour Party prior to the 1964 coup. Brizola originally wanted to reclaim the PTB name for his party, but the government awarded it to a more moderate grouping led by Ivete Vargas. The PDT joined the Socialist International in 1986. It was the major left-wing party in Brazil until the rise of the Workers' Party in 1994.