Ruling party strength is often associated with positive outcomes in autocracies, but we know little about how the effects of party strength differ across party types or which feature of party organization contributes most to better outcomes. This article argues that party infrastructural strength – the ability of grassroots party organizations to penetrate society and mobilize the masses – improves governance outcomes but only for authoritarian parties that rose to power through social movements that overthrew the existing political system. Parties that relied on mass mobilization to gain power tend to continue utilizing party strength to provide public goods and gather support. I provide empirical support for my theory using data covering all autocratic ruling parties during the post-Second World War period. The findings have major implications for understanding the intellectual and political challenges posed by well-organized one-party regimes.