Some recent studies have found little explanatory power of religious attachment to the attitude toward democracy or war in the Muslim societies. This result challenges the conventional wisdom that the religious factor is deeply connected to political turmoil in the Middle East. However, political scientists so far lack a powerful theory to explain the support of political Islam. The purpose of this article is to make a contribution in this regard with methodological rigor.

This article starts with a theoretical discussion about the concept of political Islam and the three major arguments for its popular support. Next, a research design is proposed, including the issues of conceptual definition, variable formation, data processing, and major hypotheses. Then I introduce an innovative psychometric approach, Item Response Theory (IRT), to this study. Specifically, the focus is why the application of IRT can contribute to political culture studies with methodological merit. Finally, the conclusion shows that the three explanations all explain the support of political Islam but in different aspects. People with greater personal piety or premodernist attitudes are more supportive of political Islam in attitude, but when it comes down to voting behavior, they are very rational to hold the incumbent government responsible, no matter whether Islamist parties are part of it.