Does incivility in political discourse have adverse effects on public regard for politics? If so, why? In this study we present a theory suggesting that when viewers are exposed to televised political disagreement, it often violates well-established face-to-face social norms for the polite expression of opposing views. As a result, incivility in public discourse adversely affects trust in government. Drawing on three laboratory experiments, we find that televised presentations of political differences of opinion do not, in and of themselves, harm attitudes toward politics and politicians. However, political trust is adversely affected by levels of incivility in these exchanges. Our findings suggest that the format of much political television effectively promotes viewer interest, but at the expense of political trust.