While many believe that affective polarisation poses a significant threat to democratic stability, the definition and operationalisation of the concept varies greatly. This leads to conceptual slippage as well as imprecise tests of the causes and consequences of affective polarisation. In order to clearly identify and target its micro-foundations, we must understand the degree to which political divides are, in fact, affective. In this paper, we do so. We begin by delineating affective polarisation, a social divide that is purportedly distinct from policy-based disagreements. Subsequently, we explore the influence of emotions in politics, including how affect is conceptualised within the framework of polarisation. Where possible, our literature review is supplemented with analyses of existing datasets to support our points. The paper concludes by proposing a series of questions emotion researchers could address in the study of polarisation.