This essay explores Palestinian rabbinic conceptions of idolatry or avodah zarah through examination of the Talmud Yerushalmi's treatment of Roman imperial images. The rabbinic texts reflect the prevalent Roman understanding that, alongside cultic rituals, the emperor's very assertion of political sovereignty constitutes a claim concerning divine authorization. However, while the Romans saw the latter as legitimate, the rabbis classify such claims in the category of avodah zarah. This enables us to reassess the rabbinic view of Christianity: pre-Constantinian Christianity, even if highly problematic in rabbinic eyes, would not have been seen as avodah zarah, due to its active rejection of Roman imperial ideology. By contrast, the process of Christianity's merging with imperial power after Constantine meant that, from the rabbinic perspective, Christianity now becomes idolatrous, while the Roman Empire remains idolatrous: despite the removal of 'pagan sacrifice,' political power-claims mark a key continuity in the sphere of avodah zarah.