This paper analyzes the impact of ideology on the size of US state governments. Following Pickering and Rockey (2011) this impact is hypothesized to increase with mean state income. This idea is tested using state-level ideology data derived from the voting behavior of state congressional representatives. Empirically the interaction of ideology and mean income is a key determinant of state government size. At 1960s levels of income the impact of ideology is negligible. At 1997 levels of income a one standard-deviation move towards the left of the ideology spectrum increases state government size by about half a standard deviation. Estimated income elasticities differentiated by state and time are found to be increasing with ideology and diminishing with income, as predicted by the theory.