The U. S. presidency is by design a weak office. In the United States the power of the presidency is prescribed by law, circumscribed by custom, encumbered in bureaucracy, and subject to the limits imposed by the laws of physics, economics, and politics which, in the political sphere, are as immutable as the laws of physics and more so than the laws of economics.
As much as any of these the power of the presidency is limited by the qualities of character that carry one to the presidency. We no longer elect patricians like Franklin (or Theodore) Roosevelt or great war leaders like Jackson, Grant, or Eisenhower to the presidency. I do not know why this is. I only know that it is. We have never elected a leader of the Korean or Viet Nam Wars to the presidency and we never will. At this point it appears extremely doubtful that we’ll elect a leader of the Gulf War or the war in Iraq or Afghanistan to the presidency.
We don’t elect business leaders to the presidency, either (and, increasingly, business leaders are neither entrepeneurs nor real leaders but clever rent-seekers).
We do elect celebrities, apparatchiks, the politically connected, and the politically canny. Increasingly, we elect people who perform reasonably on television.
We don’t elect people who are inclined to lead or have the experience of leading. And that lack of the virtue of leadership is an enormous limitation on the power of the president.
I make no excuses for the failures of past or present presidents. For leadership we must look to the Congress—no more inclined to or experienced at leadership than the president. And, even more frighteningly, to ourselves.