This research aims to investigate the judicial behavior of the Brazilian Supreme Federal Court (STF), which unfolds into three independent essays outlined in chapters 1, 2, and 3. The methodological approach adopted in this study is multifaceted, integrating both qualitative and quantitative techniques to provide a comprehensive understanding of the judicial performance of the STF. In the first chapter, an analysis of the STF's response to populism and authoritarianism in the Bolsonaro government was conducted, emphasizing the imperative need for democratic institutions to exert effective restraint against this threat. Through descriptive analysis, three emblematic cases from 2019 and 2020 were explored, including decisions related to the COVID-19 pandemic and controversial presidential manifestations. The study utilized the Qualitative Comparative Analysis (QCA) methodology to identify the determining variables behind these STF decisions. The results of this chapter revealed how the clash between Bolsonaro's populism and the STF influenced the court's decisions, highlighting its role as a barrier to right-wing populism, which corroborates aspects discussed in the literature review. Furthermore, the application of the QCA methodology allowed for the identification of the reasons behind the STF's anti-populist behavior, emphasizing the importance of political, ideological, and social dimensions. The second chapter investigates the relationship between the STF's decision-making behavior and the party coalitions in the Bolsonaro government, focusing on concentrated control actions related to federal laws from 2019 to 2022. The study, using a logistic model, analyzes how the strength of government coalitions influences the counter-majoritarian behavior of the STF, confirming the hypothesis that judicial independence is maximized in scenarios of political fragmentation. The results indicate a significant reduction in the probability of counter-majoritarian decisions by the STF with the strengthening of government coalitions, particularly evidenced by the alliance with the “Centrão”. Specifically, the probability of a counter-majoritarian decision by the court decreased by 86% following Bolsonaro's alliance with the “Centrão” in 2021. The third chapter is dedicated to an empirical analysis of the deference of the STF to the Public Treasury in tax cases judged under the General Repercussion from 2008 to 2023. The study employed exploratory descriptive analysis, logistic regression, and Item Response Theory (IRT) modeling techniques in addition to a literature review. The results reveal that the STF ruled in favor of the Public Treasury in approximately 59% of cases, especially when it is the defendant in the dispute. Through IRT analysis, a more pronounced deference to the Public Treasury was observed by Justices Alexandre de Moraes, Dias Toffoli, and Gilmar Mendes, while Justices Edson Fachin and Roberto Barroso demonstrated a more moderate deference. It was also seen that the STF is 86% more likely to show respect for the Public Treasury when it is the defendant in the dispute, when contributions are at issue, when the presiding minister has worked in the Federal Executive Branch before, and when the ruler leans to the center-right. The thesis at the end unifies the findings of the chapters under the guiding thread of the STF's clashes with presidential powers, through elements of the constitutional court's decision-making behavior.