The fight over NAFTA brought environmentalists into the trade debate and reinvigorated labour's commitment to trade activism. The resulting conflict has fractured the long-standing, bipartisan, pro-trade coalition in Congress and undercut US leadership to liberalize global trade. "Fast-track" legislation authorizing the president to enter new negotiations has been stymied for five years, due primarily to disagreements over whether and how to address trade's impact on labour and environmental standards. In response, this new study reexamines the trade-political landscape, showing how trade advocates and labour and environmental skeptics differ significantly in both their substantive views and their political and organizational cultures. The authors show how this new challenge differs from that of traditional trade protectionism, likening it instead to the debate a century ago over whether and how to regulate American capitalism for social purposes. The analysis leads to a series of recommendations aimed at constructive compromise and a new political foundation for US trade policy leadership.