Against the backdrop of rising global authoritarianism, this study contributes to the literature on democratic backsliding by expanding Ozan Varol’s theory of stealth authoritarianism, the use of legal mechanisms with democratic credentials for anti-democratic ends, through an in-depth investigation of surveillance legislation. It develops a theoretical framework identifying three mechanisms through which surveillance practices enable stealth authoritarianism: legitimization through crisis, executive power consolidation, and civil liberties repression. To test this framework, the paper conducts a comparative case study of the United States (2001–2018) and Türkiye (1991–2017) to find similarities as both regimes’ surveillance fostered censorship and dissent prosecution; however, a divergence as Türkiye’s total consolidation of executive power, introduction of transparent practices, and rejection of domestic and global criticism indicate a turning point from democracy to non-democracy. These findings enforce the variation of surveillance mechanisms and anti-democratic outcomes to expand current scholarship’s understanding of democratic erosion within still-democratic regimes.