We study the targeting of political advertising by presidential candidates on television. For targeted advertising to have value, the audiences for television programs must differ in meaningful ways and advertising must be effective. We estimate a model of targeted advertising. Our results suggest the function of television advertising is primarily to persuade. Moreover, we find that there is sufficient variation in 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.