We study the effects of compulsory civic duty on turnout. We take advantage of a natural experiment provided by the organization of Spanish Elections. In Spain there is a lottery to select individuals that will act as electoral administrators on the election day. Being an electoral administrator is compulsory. We study whether acting as an administrator changes turnout in subsequent elections and attitudes about democracy and elections. We find that compulsory civic duty has a strong short-term and positive effect on electoral participation but has no effect on political attitudes. This is consistent with political theories that argue that voting costs are reduced when voting habits have been developed and with psychological theories that argue that habit formation activates behaviors consistent with individuals’ underlying values without necessary changing those values.