How do local ethnic demographies affect the conduct of majoritarian elections? Because legislative elections in majoritarian systems are contested locally, local ethno‐political polarization increases the risk of pre‐election violence. Violence in such cases can be targeted with comparative ease at opposing voters, and can, if perpetrated collectively, mobilize the perpetrators’ co‐ethnics. No such dynamic is expected in PR systems where political competition plays out at higher geographical levels. Empirically, I combine new data on the ethnic composition of local populations in 22 African countries with monthly data on riots as well as survey data on citizens’ fear of campaign violence. Ethno‐politically polarized districts in majoritarian and mixed electoral systems see substantively higher (1) increases in the number of riots prior to elections and (2) levels of fear of pre‐election violence than non‐polarized districts in the same country and at the same time. Pure PR systems do not exhibit this pattern.