  We study an information design problem with two informed senders and a
receiver in which, in contrast to traditional Bayesian persuasion settings,
senders do not have commitment power. In our setting, a trusted
mediator/platform gathers data from the senders and recommends the receiver
which action to play. We characterize the set of implementable action
distributions that can be obtained in equilibrium, and provide an $O(n \log n)$
algorithm (where $n$ is the number of states) that computes the optimal
equilibrium for the senders. Additionally, we show that the optimal equilibrium
for the receiver can be obtained by a simple revelation mechanism.
