An interested and engaged electorate is widely believed to be an indicator of democratic health. As such, the aggregate level of political interest of an electorate – macrointerest – is an essential commodity in a democracy, and understanding the forces that change macrointerest is important for diagnosing the health of a democracy. Because being interested in politics requires time and effort, the article theorizes that the electorate’s level of political interest will be highest when the electorate believes the government cannot be trusted or is performing poorly. To test hypotheses derived from a proposed theory against rival explanations, the study develops a measure of macrointerest using a quarterly time series of aggregated survey items (1973–2014) of political interest. The authors find support for the theory that the electorate responds as reasonable agents when determining how closely to monitor elected officials: interest is positively related to decreases in trust in government.