We consider a multi-sender cheap talk model, where the receiver faces

uncertainty over whether senders have aligned or state-independent

preferences. This uncertainty generates a trade-off between giving suf-

ficient weight to the most informed aligned senders and minimizing the

influence of the unaligned. We show that preference uncertainty dimin-

ishes the benefits from specialization, i.e., senders receiving signals with

more dispersed accuracy. When preference uncertainty becomes large,

it negates them entirely, causing qualified majority voting to become

the optimal form of communication. Our results demonstrate how po-

litical polarization endangers the ability of society to reap the benefits

of specialization in knowledge.

Keywords: cheap talk, information aggregation, specialization in knowl-

edge, voting