We study the targeting of political advertising by presidential candidates on television. Targeting strategies for television differ from targeting strategies for direct mail advertising or get out the vote efforts because candidates cannot target voters individually. Instead, candidates must target television programs with viewers most similar to the desired target voters. Thus, for targeted advertising to have value, the audiences for television programs must differ in meaningful ways and advertising must be effective. We develop and estimate a model of targeted advertising. We study whether television shows segment potential voters sufficiently to allow for effective targeting and we consider the effect of television advertising-whether it persuades individuals to vote for a particular candidate or mobilizes them to vote in general. Our results suggest the function of television advertising is primarily to persuade. Moreover, we find that there is sufficient variation in the distribution of viewer characteristics across television programs to allow for effective targeting. The most effective targeting strategies therefore involve both parties adopting similar strategies of advertising primarily on programs with audiences containing many swing voters. Actual candidate behavior is largely consistent with this strategy indicating that candidates seem to accurately believe that the function of television advertising is to persuade voters. Nonetheless, we are able to uncover specific ways in which candidates could improve their advertising by identifying particularly effective shows and by quantifying the tradeoff between cost and effectiveness.