Why Civil Wars are Fought By Extremists: Polarization, Abstention and the Cost of Participation

Why are civil wars fought by extremists rather than moderates? The median voter theorem holds that organizations contesting for power will shift to the center of the ideological spectrum to maximize their support. Such models assume that supporting means voting and that it is relatively costless. When it is costly for individuals to support organizations contesting for power, such as in civil war contexts, the central tendency is constrained by the cost of participation. In equilibrium, those to either extreme are more likely to participate, moderates tend to abstain. The range of moderates who abstain grows larger the more costly participation becomes. I develop a spatial model of participation that exhibits these features and discuss its implications in the case of the civil wars in Central American in the 1970s and 1980s and Syrian Civil War.