Despite prior research on political capabilities and their relationships with meaningful outcomes at work, it remains unclear why certain employees are incapable of successfully navigating workplace politics. To clarify this, our research develops and validates a measure of political self-efficacy at work (PSEW) across seven independent and varying samples. Evidence from faculty members and subject-matter experts in Study 1 provides initial support for the content validity of the new PSEW scale. Then, in Studies 2 and 3, we employ two separate samples to confirm the scale’s convergent and discriminant validity and factor structure. We repeat this process, in Study 4, on several new nomological neighbors (e.g., the Dark Triad traits, general political behavior, impression management, and political will). In Studies 5 and 6, using multi-wave and multi-source data, we assess the criterion-related and predictive validity of the PSEW scale, and in Study 7, we test our full theoretical model. Altogether, these findings verify the nomological network and validity of the new PSEW measure and provide theoretical and practical developments surrounding organizational politics.