Paiva's political career began to rise in October 1962, when he was elected Congressman for the State of São Paulo by the Brazilian Labour Party. He took office in February of the next year and participated in the Investigation Committee created to examine the activities of both the Institute for Social Research and Studies (Instituto de Pesquisas e Estudos Sociais) and the Brazilian Institute for Democratic Action (Instituto Brasileiro de Ação Democrática). Those two organizations were supposedly funding commentators and writers who warned about the "red menace" in Brazil. The Committee discovered that some checks were being deposited in the accounts of military officers; this scheme was sponsoring the upcoming coup d'état. With the 1964 coup, Paiva had his mandate revoked by the junta on April 10, 1964.