The founding members of the PKP came from members of the "Partido Obrero de Filipinas", a labor-centered party formed in opposition to the leading Nacionalista and the Democrata parties at the time. Most of the members of the Partido Obrero were also leading figures in the labor movement, including PKP founders Crisanto Evangelista, Antonio Ora, Jacinto Manahan, and Domingo Ponce. Evangelista and his group were increasingly being radicalized towards left-wing politics through their increasing involvement with the Comintern, Profintern, and the CPUSA. Particularly, in 1928, Evanglista, Manahan, and Cirilo Bognot went to the Soviet Union to attend the Profintern's Fourth Congress. These people were also leading figures in the Congreso Obrero de Filipinas, the leading trade federation at the time.