Political turnover and the accumulation of democratic capital*

•The stability of strong executive constraints in democracies under powerful incumbents is studied.•Powerful incumbents prefer weak constraints, and vice-versa.•To prevent institutional reform, incumbents always invest in the society's democratic capital.•Higher levels of democratic capital protect against the adoption of weak constraints.

Certain democratic institutions tend to persist in some countries whereas they are frequently reversed in others. Focusing on strong constraints on executive power as one such institution, this paper theoretically studies the cross-country differences in the costs of relaxing these constraints. The model features two political parties that stochastically alternate in office according to a political uncertainty parameter. In each period, the incumbent can make reversible investments into the future government's ability to reform executive constraints. The main results indicate that more competitive elections and higher degrees of policy polarization between the political parties lead to high and persistent levels of investment into the society's stock of “democratic capital”. These higher costs of institutional reform in turn result in durable strong executive constraint-regimes.