Abstract: The standard consequentialist analysis of constitutional law focuses on the incentives that shape the behavior of government officials and other constitutional actors. Incentive-based accounts justify elections as a means of constraining officials to promote the public welfare, or at least the welfare of the median voter; justify the separation of powers as a means of making "ambition counteract ambition"; justify negative liberties, such as free speech and free association, as a necessary corrective to incumbent officials' incentives to suppress political opposition; and so forth. In this experimental Essay, I offer a preliminary sketch of a different way of looking at constitutional law generally and constitutional structure in particular: through the lens of "selection effects." Constitutional rules, on this account, should focus not only on the creation of optimal incentives for those who happen to occupy official posts at any given time, but also on the question which (potential) officials are selected to occupy those posts over time. Where an incentive analysis is short-term and static, asking only how legal rules affect the behavior of a given set of officeholders, selection analysis is long-term and dynamic, asking how legal rules themselves produce feedback effects that, over time, bring new types of government officials into power. This turn to selection-based analysis yields fresh insight into the dynamics of constitutionalism. Because constitutional rules affect the pool of potential and actual officeholders, as well as the behavior of current officeholders, focusing on selection effects shows that some constitutional rules prove "self-stabilizing": the rules tend to select a corps of officeholders who will act to uphold and stabilize the rules themselves. Other constitutional rules, by contrast, prove "self-negating": the rules tend to select a corps of officeholders who work to undermine or destabilize the rules themselves. This framework supplies insights into diverse areas of constitutional law and theory, ranging from governmental structure, campaign finance, and voting rights to criminal sentencing, free speech, and affirmative action.