Kerala has one of the most stable party systems in India, and represents a clear exception to the Indian norm of volatility, instability and electoral change. In this article, we explore the geographical structure of this stability, and examine the extent to which current political divisions are a reflection of the divisions that existed at the inception of mass democracy in Kerala more than 50 years ago. First, we examine the extent to which historical legacies of party formation shape contemporary patterns of voting behaviour. Second, we examine the extent to which these historical legacies were established along social lines to do with caste, religion and class. Finally, we discuss the implications of these results.