In a useful conversation... there is a double coincidence of wants. You have to be interested in what I have to say; I have to be interested in what you have to say. This is an important reason why people with conventional interests seem more socially intelligent. Even if they don't check whether their audience cares, it probably does.

What happens if fully rational politicians compete for the support of irrational voters — specifically, voters with irrational beliefs about the effects of various policies? It is a recipe for mendacity.