Within the extensive literature on political moderation the impetus for opposition movements to moderate their political behaviour is depicted as being driven by either inclusion into or exclusion from institutional and electoral politics. The result being that two analytical camps have developed that treat the drivers and vagaries of moderation in distinctive and mutually exclusive fashions. While each camp produces cogent and nuanced analyses of the moderation process, the lack of any analytical consensus further complicates our understanding of the moderation process overall, and ultimately precludes the generation of a universally accepted and generalisable theory to account for the progressive moderation of opposition movements. However, this paper seeks to challenge the utility of such an analytical dichotomy. Using the behavioural shifts of the Palestinian Islamist movement Hamas since 2004 as its case study, this paper demonstrates that the impetus for shifts in Hamas’s political behaviour during this period has come from a combination of both inclusive and exclusive political forces. Analysing primary source documents, leadership statements and interviews, and public polling data this qualitative study demonstrates that from 2004 – 2006 political inclusion was the dominant driving force behind Hamas’s progressive moderation. However, after Hamas’s surprise election victory in 2006, political exclusion became the dominant driving force for Hamas’s continuing moderation after Israel imposed a siege on Gaza designed to exorcise Hamas from Palestinian politics. What the subsequent analysis reveals is that during the inclusion phase Hamas could adopt less ideologically risky policy positions such as forming a political party, publishing an election manifesto, and contesting municipal and parliamentary elections. However, during the post-election exclusion phase, Hamas was forced to adopt more ideologically risky policy positions by making significant ideological compromises on core areas of its raison d’être, namely having to refine its refusal to recognise the Israeli state, re-think its opposition to the two-state solution, and modulate its armed resistance to Israeli occupation of the West Bank, Gaza Strip, and East Jerusalem. Overall, the paper highlights the need to closely study the effect(s) of changes in the political environment within which an opposition movement operates and how that movement responds to understand key drivers of the moderation process. Equally, the paper highlights the need to understand how a movement justifies its response to these changes to its constituencies to avoid any internal schism or retreat from the moderation process.