It is commonly accepted that social dominance orientation (SDO) and right-wing authoritarianism (RWA) are potent unique predictors of a variety of prejudice and prejudice-related constructs. However, contrary to some predictions, there has been little evidence that these constructs interact to produce this outcome—they appear to be additive but not interactive in their prediction of prejudice. We extend the interaction hypothesis to consideration of another broadly relevant construct—political ideology. Drawing from 14 independent New Zealand–based samples, we show, through meta-analysis and multilevel random coefficient modelling, that SDO and RWA additively and interactively predict levels of political conservatism operationalised in a variety of ways. Specifically, both constructs are associated with increasing political conservatism, and the lowest levels of conservatism (or highest levels of political liberalism) are found in those lowest in both SDO and RWA.