This study offers a novel investigation of why incumbents from the proestablishment coalition in an authoritarian regime do not have an electoral edge over challengers. Although proestablishment incumbents in nondemocratic regimes, as in democracies, enjoy advantages in the form of distribution of patronage, pork barrel, and privileged access to media, in a competitive election in such regimes there is no guarantee of their reelection. While one might expect the incumbent reelection rate in a nondemocratic regime such as Iran to be high, based on the results of Iranian parliamentary elections, the incumbent reelection rate is relatively low (33%). By focusing on Iranian parliamentary elections since 1980 and by using original data gathered at the district level, I have found that incumbents from the nonestablishment coalition have an electoral edge over proestablishment candidates. In spite of manipulative strategies by the ruling incumbents (e.g., banning candidates, intimidating voters, and forging ballots), the likelihood of independent and reformist incumbents winning has risen. The results of last three consecutive parliamentary elections in Iran (2004, 2008, 2012) illustrate that the nonestablishment incumbents have had more capacity to respond to voters’ demands. Furthermore, I have found that electoral institutions have an effect on the level of incumbency advantage in these elections. By placing Iranian’s mixed electoral systems in a comparative context and exploring the effect of electoral institutions on voting behavior, I have found that the incumbency advantage is greater in single-member districts than in multimember districts. Studying elections in authoritarian regimes can help to explain why, despite strong social demands in many polities for democratization, serious challenges to democratic transition remain. This study expands on the research on the electoral behavior of citizens and institutions in nondemocratic states.