This article, employing an interpretive and inductive approach with a qualitative comparative method, investigates and contrasts the perspectives of two prominent thinkers of the Muslim Brotherhood, namely Hassan al-Banna (the founder) and Rashid al-Ghannushi (leader of the new generation), regarding the concepts of "party" (Hizb) and "partisanship" (Tahazzub) within the Islamic political system. The central question is whether the ideological differences between these two representatives of the Brotherhood's intellectual evolution across two distinct historical periods can be attributed to temporal, spatial conditions, and socio-political transformations. Through content analysis of primary sources (works of al-Banna and al-Ghannushi) and secondary resources, the research findings indicate that while both emphasize the unity of the Ummah and the comprehensiveness of Islam, al-Banna, operating within the colonial context of Egypt, held a negative view of partisanship, considering it a source of division and societal weakening rooted in Western political concepts. Conversely, al-Ghannushi, shaped by experiences of exile in Egypt and France and witnessing Tunisia's democratic transition, perceived partisanship as a tool for political participation and achieving power within an Islamic framework, eventually leading the Ennahda Movement to formally become a political party. These differences largely stem from the contrasting political and social environments where these thinkers lived and were active, as well as evolving perceptions of the role of parties in modern societies. Al-Banna emphasized an organic Islamic society rejecting Western-style parties, whereas al-Ghannushi, influenced by democratic realities, integrated party politics into his Islamic framework. Therefore, the evolution of Brotherhood thought from a resistance movement to an established political force signifies an ideological flexibility in adapting to new realities, reflecting the dynamic nature of political Islam.