Political parties in constitutional theory

In this chapter, I first argue that the key function that parties perform, when functioning as they ought to function, is to facilitate a mutually responsive relationship between public policy and popular opinion by acting as an intermediary between a state and its people. They perform this intermediary function in a unique manner, because of their bi-directionality and their plenary character. When they perform this function effectively, political parties significantly reduce four key information and transaction costs that would otherwise make democratic governance impossible: political participation costs, voters’ information costs, policy packaging costs, and ally prediction costs. I further identify four normative principles in relation to political parties: viz, the purposive autonomy principle, the party system optimality principle, the party-state separation principle, and the ‘anti-faction principle. These political principles are drawn from the value of democracy itself. As such, they should – alongside other relevant political and constitutional norms – inform fundamental constitutional design choices.