Norm challenge is a continuous feature of international norms. However, the dynamics of such a challenge are still not properly understood. Therefore, this article examines in-depth the key processes involved in a major, but still underexplored challenge in the case of the nuclear non-proliferation regime: the recent accommodation of India in the regime, even though it developed nuclear weapons in violation of the regime's fundamental non-proliferation norm. More specifically, it will focus on how certain states came about to support such a norm challenge. In this regard, the European Union and its member states played a crucial role, as they included both very supportive and very reluctant states that all had the opportunity to block India's accommodation in the regime. In contrast to the traditional focus on persuasion and argumentation in the norm-based literature, this article argues that it was the peculiar interplay of persuasion and argumentation with material incentives, pressure, and bargaining that created the support for norm challenge in the early stages, in particular in the case of the states that remained highly sceptical of the challenge.