It is useful to note three major presidential duties of broad scope that are explicity recited in the Constitution: "to take Care that the Laws be faithfully executed," to "faithfully execute the Office of President of the United States" and to "preserve, protect, and defend the Constitution of the United States" to the best of his ability. The first is directly imposed by the Constitution; the second and third are included in the constitutionally prescribed oath that the President is required to take before he enters upon the execution of his office and are, therefore, also expressly imposed by the Constitution.
The duty to take care is affirmative. So is the duty faithfully to execute the office. A President must carry out the obligations of his office diligently and in good faith. The elective character and political role of a President make it difficult to define faithful exercise of his powers in the abstract. A President must make policy and exercise discretion. This discretion necessarily is broad, especially in emergency situations, but the constitutional duties of a President impose limitations on its exercise.
The "take care" duty emphasizes the responsibility of a President for the overall conduct of the executive branch, which the Constitution vests in him alone. He must take care that the executive is so organized and operated that this duty is performed.