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

How do party representatives as poll workers at electoral tables (voting booths) affect elections? Paraguay’s system of counting votes is partisan and adversarial. Every booth has three poll workers which are, by law, party representatives. In theory, multiple parties count votes at each booth, ensuring the integrity of elections. In practice, there are stark inequalities in partisan poll worker representation during the 2018 Paraguayan elections we study. We exploit a natural experiment to show that partisan poll workers decrease an opposing party's vote share by up to 2 percentage points (pp) and increase theirs by up to 1 pp. We also demonstrate how incentives for electoral manipulation vary by electoral system. Partisan poll workers collude more often with rival party poll workers within proportional representation races, as distributing votes among themselves can help their parties earn more seats for their legislative candidates. Instead, single-winner plurality voting yields less collusion.