At an abstract level, it is easy to make an argument for the virtue of an effort to isolate and examine the impact of party structure. Political parties are the great intermediary institutions of democratic politics. Yet they inevitably transform and not just transmit public wishes. It is hard to imagine how their internal structure would not be central to that transformation. So the effort to unpack these influences should be inherently virtuous, that is, intrinsically connected to question of policy responsiveness and democratic representation. Yet the moment this effort shifts to the operational level, embedding a theoretical argument in the practical details of American politics, problems surface, likewise inherently.