[5] In 2018, he attempted to run for President of Brazil as a member of the Socialism and Liberty Party (PSOL), but was rejected during the nomination process in favor of labor leader Guilherme Boulos.

Arruda Sampaio Jr. attended the School of Economics, Business and Accounting of the University of São Paulo (FEA-USP), where he completed his undergraduate education.

[10] During the COVID-19 pandemic in Brazil, Arruda Sampaio Jr. advocated for social distancing measures coupled with economic relief to stop the spread of the virus.

[11] Plínio de Arruda Sampaio Jr. ran for municipal office in São Paulo in 2004 as a member of the Workers' Party (PT).

[18][19] Labor leader Guilherme Boulos, who eventually received the party's nomination, was seen by Arruda Sampaio Jr. as being too close to former President Luiz Inácio Lula da Silva.