This chapter presents qualitative case studies of the dramatically different political dynamics of TPP and TTIP negotiations. Why was lobbying so much more contentious over TPP while lobbying over TTIP was muted and almost entirely in favor of the agreement? The chapter traces the development of industry and labor union positions on each agreement, showing how the effects of endowments-based, inter-industry trade on the basis of comparative advantage (much more prevalent with TPP partners) serves to unify industries and unions around their particular position, facilitating strong collective action. With TTIP, the chapter shows how internationally engaged firms were highly motivated to lobby in favor of increased market access and the removal of regulatory barriers, while domestic-oriented firms either sat out of the political process entirely or formed cross-sectoral ad hoc coalitions. These cases elucidate how and why actors came to these decisions.