Exchange rates reflect macroeconomic fundamentals, which in turn are regime dependent. In politically unstable countries, expectations of regime change can have a significant impact on exchange rate dynamics. We exploit Argentina’s unexpected 2019 primary election results as a natural experiment to gauge the impact of a change in such expectations. When populist candidate Alberto Fernández’s victory margin (15.6%) doubled pre-election polling predictions (7.2%), financial markets immediately recalculated the probability of a change in regime. Using parallel market exchange rates, we estimate that the real exchange rate differential between populist and non-populist regimes exceeds 100%. This large gap creates extreme political sensitivity: regime change expectations of 7-16% can trigger 10% exchange rate movements. Our findings help explain persistent exchange rate volatility in emerging economies and highlight the limitations of purely macroeconomic stabilization approaches when political sustainability is uncertain.