Affective polarization has emerged as an important construct in the literature on partisanship. However, most efforts to measure it have relied on simple preexisting indices, potentially missing the complexity of affective polarization. In this article, we address these concerns by reconceptualizing and deriving a new measure of affective polarization. Drawing on the notion of political sectarianism and other lines of research in political behavior and social psychology, we develop and validate a novel multidimensional measure of affective polarization consisting of three parts: othering, aversion, and moralization. Our analyses yield a valid and reliable nine-item measure with three subdimensions. These subdimensions and the full scale broadly correlate with various measures of political identity, anti-democratic elite action, and political violence. Importantly, we find that the subdimensions have different patterns of correlation with key criterion variables, suggesting that othering, aversion, and moralization are distinct components of affective polarization.