We study the dynamic selection of governments. A government consists of a subset of the individuals in the society. The competence level of the government in o ce determines collective utilities (e.g., by determining the amount and quality of public goods), and each individual derives additional utility from being part of the government (e.g., corruption or rents from holding o ce). We characterize the dynamic evolution of governments and determine structure of stable governments, which arise and persist in equilibrium. Our main focus is on the impact of di erent political institutions on the selection of governments. Perfect democracy, where current members of the government do not have an incumbency advantage or special powers, always leads to the emergence of the most competent government. However, any deviation from perfect democracy destroys this result. There is always at least one other, less competent government that is also stable and can persist forever. In addition, even the least competent government can persist forever in o ce. When there are stochastic shocks to the competence levels of di erent governments or to the rules determining the election of new governments, political institutions with a greater degree of democracy (less power for incumbents) are shown to perform better, because they can adapt to changes more successfully. This suggests that a particular advantage of democratic regimes is their relative exibility. We also show that, in the presence of stochastic shocks, \\royalty-like" dictatorships may be more successful than \\junta-like " dictatorships, because they might also be more adaptable to change.