Democratic publics have always struggled to constrain their elected leaders’ foreign policy actions. By its nature, foreign policy creates information asymmetries that disadvantage citizens in favor of leaders. But has this disadvantage deepened with the advent of the Internet and the resulting fundamental changes in the media and politics? We argue that it has. The current information and political environments erode constraint by inclining constituents to reflexively and durably back “their” leaders and disapprove of opposition. These changes make it harder for citizens to informationally “catch up” with and constrain leaders because views that contradict citizens’ beliefs are less likely to break through when media are fragmented and siloed. These changes have important implications for theories concerning the democratic peace, audience costs, rally effects, and diversionary war. They may also contribute to instability in foreign policy by contributing to sudden and destabilizing changes in public opinion that undercut commitments abroad.