Clientelist parties (or political machines) engage in a variety of strategies during elections. Most studies focus exclusively on "vote buying," a strategy that rewards opposing voters for switching their vote choices. Yet in many countries, machines also adopt other strategies, such as activating their passive constituencies through "turnout buying." What factors explain variation in patterns of clientelism during elections? We develop an analytical framework and formal model that emphasize the role of individual and contextual factors. Political machines focus on two key attributes of individuals--political preferences and inclination to vote--when choosing their mix of clientelist strategies. Machines also tailor their mix to at least five contextual factors: compulsory voting, machine support, political polarization, salience of political preferences, and strength of ballot secrecy. Evidence from Argentina, Brazil, and Russia is consistent with these findings.