The Transatlantic Trade and Investment Partnership (TTIP) negotiations have become the center of debate in EU trade policy, where the European Commission and civil society organizations are key actors. This paper argues that a key reason why TTIP has become so controversial has to do with the nature of the arguments used by each side. The main arguments in favor of TTIP emphasize the economic and geostrategic benefits. The main criticisms of TTIP focus on its alleged negative impact on product safety and public policies. Identifying the foundational assumption(s) behind these arguments, we show that this debate is special because opponents and supporters' premises emerge from assumptions based on different perspectives: while opponents assume that the EU will succumb to neoliberal American preferences, supporters focus on the US-EU combined market power vis-à-vis third countries. Since these assumptions do not necessarily contradict each other, the debate is less whether benefits outweigh costs and more whether such costs are probable, leaving the supporters with a defensive position. This is an important distinction in explaining why opponents dominate the public debate. Our findings also indicate, however, that opponents' thesis has been successful because the US is the partner; such public mobilization is less probable on other trade agreements.