Getting a seat at the table: Partisan poll workers and electoral bias

Does poll workers' partisanship affect electoral outcomes? Many countries use partisan and adversarial vote-counting systems where poll workers are party representatives and mutual control is expected to provide fairness. Yet in countries with established party regimes, parties often have de facto unequal capacities to send representatives to all booths. Exploiting quasi-random assignment of voters to booths in Paraguay's 2018 general elections, we estimate that partisan poll workers decrease an opposing party's vote share by up to 1.1 percentage points (pp) and increase theirs by up to 0.7 pp. Our analyses also expose differential effects according to the electoral system.  In proportional representation races, established parties have incentives to increase their support at the expense of smaller parties.  In contrast, single-winner plurality races dampen this effect due to the winner-take-all aspect of these races. Our results have practical implications for politicians and policymakers, and theoretical implications for elections in developing democracies.