In contrast to the specificity with which the Constitution outlines the powers of the legislative branch, the powers of the presidency are vaguely described. The Framers designed the presidency so that power could flow to the executive in times of national crisis, but recede as the emergency faded. More than two centuries later, conflict persists between Congress and the presidency over which institution has the power to make national policy.

For most of the nineteenth century, presidents typically played a small role in the day-to-day operations of government. Presidents spent much of their time overseeing the dispensation of federal appointments to fellow partisans. Many important decisions were delegated to cabinet officers who interacted as much with Congress as the White House. Throughout the twentieth century, presidents assumed greater administrative responsibilities, transforming the office in ways the Framers would scarcely recognize.

The modern presidency subsumes several roles. The president is both head of state and commander in chief of the U.S. armed forces. Recent presidents have used their authority to make agreements with foreign powers and send U.S. troops into battle without congressional approval. The president has also assumed firm control of a vast national administrative apparatus. Congress has delegated many administrative functions to the presidency, including responsibility for drafting a federal budget. Finally, presidents have enhanced their legislative role, issuing controversial executive orders, making use of veto threats and signing statements, setting forth an agenda to guide the legislative branch, appealing to the public for support, and crafting political coalitions to see initiatives through the lawmaking process.

As their responsibilities increased, presidents acquired greater staff and resources. Nonetheless, the mismatch between the expectations and powers attached to the office remains the fundamental dilemma facing modern presidents. Successful presidential leadership requires a mixture of luck, political skill, and careful deployment of resources—be it reliance on the veto and other formal powers, leveraging popularity, or making judicious use of administrative capacities.