Clientelism is frequently observed in our societies. Various mechanisms that help sustain incomplete political contracts (e.g., monitoring and punishment) have been studied in the literature to date. However, do such contracts emerge in elections with secret ballots when the interactions are one-shot? How does repetition affect the evolution of incomplete political contracts? Using an incentivized experiment, this article finds that even during one-shot interactions where monitoring is not possible, candidates form incomplete contracts through vote buying and promise-making. The candidates’ clientelistic behaviors are heterogeneous: some target swing voters, whereas others offer the most to loyal voters, or even opposition voters. These tac...