How do autocrats mitigate the threat of opposition within their governments? While rulers can alienate rivals by expelling them from the governing coalition, this strategy can trigger further instability. Existing research indicates that rulers strategically target their most threatening rivals. The literature identifies non-partisan and non-coethnics as significant threats to the regime. However, the absence of organized opposition parties or ethnic opposition in repressive autocratic regimes does not imply a lack of political threats. I contribute to the existing literature by arguing that political cleavages emerging from previous periods of political mobilization pose an enduring political threat to autocratic rulers. The empirical analysis focuses on former French Sub-Saharan African colonies, where one-party rule followed a brief electoral competition period before independence. I show that ethno-political cleavages, which became politically salient during colonial elections, affected the vulnerability of post-colonial ministers to purges. Due to the high risks involved in purging, I expect rulers to target historically mobilized non-coethnics at points in their rule where the cost of inaction and the ruler's strength are high, such as following an unsuccessful coup. The analysis relies on newly collected data on political mobilization during late-colonial elections and individual-level data on post-colonial ministers between 1966 and 2016. Using a difference-in-difference design, I show that ministers from ethnic groups that mobilized politically at decolonization faced an increased risk of being purged following unsuccessful coup attempts. The results indicate the long-lasting nature of ethno-political cleavages that became salient during late colonial elections.