Do gains from globalization erode support for economic nationalism? We study how North American Free Trade Agreement (NAFTA)‐enhanced local access to US markets affected Mexican demands for protectionist platforms. The left—led by Andrés Manuel López Obrador (AMLO)—underperformed in cities benefiting from export‐access gains during the 2006 presidential elections. This effect is observed strictly in 2006—the only post‐NAFTA election in which debates over trade integration played a salient role. Our findings are robust to controls for import‐competing pressures from NAFTA and the China shock. AMLO's 2006 protectionist platform likely cost him that year's election, and campaign media strategies in 2012 map to this earlier backlash.