In Brazil’s highly fragmented party system, the Workers’ Party (PT) is the country’s largest and most institutionalized party. Following its origins in São Paulo’s 1980s union movement, the PT has won five of the last six presidential elections. The PT has also been uniquely successful in creating attachments with voters. In fact, on average, one in ten Brazilian adults sympathized with the party from 2008 to 2018. This article uses six AmericasBarometer to explore the individual-level determinants of partisanship with the PT and other parties before and after President Dilma Rousseff’s 2016 impeachment. We test three hypotheses that associate partisanship with the PT to leftwing ideological identification, grassroots organizations, and conditional cash transfers. Our findings reveal that the determinants of partisanship are strikingly similar to those of other parties, supporting the claim made elsewhere that the PT is an institutionalized party without roots in society.