This article assesses two main theories of the decline of political support that is found in many western democracies. The first is society centred and built on the concepts of social capital, trust and civil society. The second is politics centred and focuses on the performance of government and the economy. The two theories are not necessarily incompatible, but they are usually treated in a mutually exclusive way. In this article they are tested against a combination of aggregate cross-national comparative data and detailed case studies of four countries that have suffered exceptional decline of political support for politicians, political institutions and the systems of government. The puzzle is that cross-national comparative evidence about a large and diverse number of nations supports social capital theory, whereas in-depth study of four countries that have experienced substantial decline of political support does not. The erosion of support coincides in all four with poor economic and/or political performance. A way of reconciling the two theories and their supporting evidence is suggested, arguing that while social capital is a necessary foundation for democratic support, it is not a sufficient cause.