This study attempts to assess the different ways through which Islam as a religion can impact politics. In fact, the notion that is collectively labeled as Islam and its re-interpretation as an escalating presence of religion in politics in today's world has deep layers. To distinguish a variety of these layers, each with different characteristics, they should be defined, and the type of contributions they can make to politics should be examined one by one. Mixing up the layers with each other and employing characteristics of one for another can result, and in fact has resulted in many misunderstandings in political discussions. In order to show how to distinguish the layers and how to find the dominant layer of religion in each case, the role played by Islam in three important Islamic countries: Iran, Saudi Arabia and Turkey will be examined. Comparing and contrasting these cases, this paper will conclude that only through identifying layers of religion in force and distinguishing the dominant ones can the actual role of religion be examined in each case study.