This article provides an explanation of major civil upheaval and violent political turmoil – hereinafter referred to as “active political factionalism” – that take place in the Mexican state of Oaxaca. More specifically, this work identifies the main causes of extra-institutional protest politics or uncivil modes of political action that seriously affect political stability and undermine democratic advancement. The analysis focuses on the effects of two groups of explanatory factors: i) deteriorated socioeconomic conditions (such as poverty and inequality), and ii) institutional limitations (corruption, electoral exclusion, a weak rule of law, among others) in a context of “subnational authoritarianism.” The study also examines some of the mechanisms through which these variables operate and interact with other factors (resources, opportunities, government actions, etc.) to generate political factionalism. This work finally assesses the relative importance of these two groups of explanatory factors. Evidence presented here shows that institutional factors are the primary sources of political factionalism in Oaxaca, while socioeconomic factors are quite significant but not predominant.