In a symmetric information voting model, an individual (information controller) can influence voters’ choices by designing the information content of a public signal.
We characterize the controller’s optimal signal. With a non-unanimous voting rule, she exploits voters’ heterogeneity by designing a signal with realizations targeting different winning-coalitions. Consequently, under simple-majority voting rule, a majority of voters might be strictly worse off due to the controller’s influence. We characterize voters’ preferences over electoral rules, and provide conditions for a majority of voters to prefer a supermajority (or unanimity) voting rule, in order to induce the controller to supply a more informative signal.