An important aspect of executive power in times of crisis is the large variation in presidential performance between different administrations. As I explained in my last post on this subject, the top echelon of the executive branch is usually controlled by just a small group of people – the president himself and a few trusted advisers. In addition to the points I made in that post, this reality has one more crucial implication: we can expect much greater variation in the quality of presidential performance than in that of other branches of government, especially Congress.
Basic statistical theory shows that, holding other variables constant, small samples are likely to vary more than large ones drawn from the same underlying distribution (group of people or things). Just by random chance, the former are likely to deviate far more from the mean and the median. For a technical explanation, see this discussion of the law of large numbers. In this case, the underlying distribution is, roughly speaking, prominent American politicians, and presidents are the small sample group, while members of Congress and justices of the Supreme Court are relatively larger samples (in the case of Congress, with its 535 members, much larger).
The downside of this is that it makes it far more likely that a given administration will display extremely poor performance than a given Congress. In the last 40 years alone, I would suggest that we have had at least three administrations with extremely poor performance due to incompetence at the top (Jimmy Carter, George W. Bush) or venality (Richard Nixon). Those who differ from me on the ideological spectrum will probably disagree with me on some of these cases. But few are likely to have a list of extremely poor presidents that is much shorter than mine.
The unusually high variation of presidential performance suggests that even if Eric Posner and Adrian Vermeule are right (as I believe they are) to argue that the executive is on average more competent to manage crises than Congress and the Supreme Court, it does not necessarily follow that the other branches of government should give broad deference to executive decisions. We also have to take into account the damage caused by those cases where executive decisionmaking is far worse than that of the other branches due to the fact that the administration in power is unusually incompetent, unusually venal, or both.
To be sure, the high variation in presidential performance suggests that we are also more likely to have an extraordinarily good president than an equally wonderful Congress or Supreme Court. As against Carter and George W. Bush, we can set George Washington, Abraham Lincoln, and a few others who managed crises extremely well. Ultimately, this aspect of the executive power debate comes down to a question of whether we have more to fear from extremely bad executives than hope from extremely good ones. As a libertarian, I definitely come down on the side of fear rather than hope when it comes to government power. In my judgment, a very bad president can do far more harm in a crisis than a very good president can do on the other side of the scale.
Moreover, even in a nondeferential system, an unusually competent executive will generally be able to build up sufficient political capital that Congress and the Supreme Court will be reluctant to challenge him too much in a crisis even if they retain the authority to do so. Thus, an unusually competent executive should be able to manage crises relatively well even if the other two branches retain considerable power to constrain him. On the other hand, such countervailing power can play a valuable role in limiting the damage done by an unusually bad president.