Low levels of trust in government have potentially wide-ranging implications for governing stability, popular legitimacy, and political participation. Although there is a rich normative and empiricial literature on the important consequences of eroding trust in democratic societies, the causes of political trust are less clear. In this article we estimate the effect that changing Americans' views about the perceived honesty and integrity of political authorities (or "political probity") has on their trust in government using randomized survey experiments. In one experiment on a convenience sample and a direct replication on a more representative sample, we find that a single Op-Ed article about political probity increased trust in government by an amount larger than the partisan gap between Democrats and Republicans. These results complement prior observational studies on trust in government by demonstrating that political probity plays an important causal role in shaping Americans' judgments about the trustworthiness of their government and politicians.