On 4 June 1943, a military coup crushed Argentina's democracy, marking the end of the oligarchic era and ‘planting the seeds’ of Peronism. This case sheds light on how rulers’ mistakes can operate as a key independent variable in producing regime changes. We argue that the former conservative president, Ramón S. Castillo, provoked an otherwise avoidable democratic breakdown. Specifically, Castillo's misguided relationships with regime insiders and outsiders unintentionally eroded political stability and triggered the fall of democracy. Until now, agent-based scholarship has fallen short in tracing incumbents’ mistakes and linking them to regime-change processes. We test the argument by conducting a within-case analysis of Argentina's democratic fall in the early 1940s, scrutinising the president's errors at five critical events. We conclude that critical-event analysis can help disentangle the role of leaders’ mistakes in other episodes of regime change.
