Parties have emerged as a central concern of comparative constitutional law, and for good reason. Parties should be at the forefront of descriptive analyses of how constitutions function. In practice, for instance, the separation of powers depends heavily on the shape of the party system, as do many other aspects of constitutional performance.1 Moreover, breakdowns of party systems have been a significant factor in explaining recent episodes of democratic erosion or breakdown.2 In other words, crises of liberal democratic constitutionalism are often caused by crises in party systems.

But what is more challenging is developing a normative theory linking constitutions and parties. In other words, to what extent can constitutions (or comparative constitutional law) prevent or fix breakdowns in party systems? On that question, this chapter offers some skepticism, or at least outlines a series of challenges.

Section 17.2 develops a brief map of the different ways in which party systems break down.