Final answer:
Presidents Ronald Reagan, Bill Clinton, and George W. Bush each faced constitutional questions about the limits of executive authority. Reagan during the Iran-Contra Affair, Clinton during his impeachment proceedings and assertion of executive privilege, and Bush in matters related to national security and executive powers. The controversy over these issues reflects ongoing debates about the separation of powers and the evolution of presidential authority.
Step-by-step explanation:
Throughout American history, presidential powers have often been a point of contention and constitutional interpretation. Ronald Reagan faced constitutional questions during the Iran-Contra Affair about whether the executive branch had overstepped its bounds with respect to congressional power, specifically a congressional ban on military aid which was circumvented. Reagan's presidency raised questions about the extent of Presidential power to "protect national interests" versus Congress's authority to oversee executive actions.
Bill Clinton's impeachment proceedings centered on issues of personal misconduct, arising from the Monica Lewinsky scandal and further involving the use of executive privilege. Clinton asserted executive privilege, but the Supreme Court has limited this power, especially when it is used to avoid prosecution.
George W. Bush also faced scrutiny with regards to the executive power amid the Global War on Terror. The scope and limits of executive authority over national security, the use of veto power, and the National Security Council were all areas of intense debate and sometimes criticism during his administration.
Presidential powers have evolved over time, often expanding in response to various crises and the growth of government services and bureaucracy. While some powers are directly from the Constitution, others have developed out of necessity. However, a president's use of unilateral actions, such as executive agreements or executive orders, remains controversial and reflective of the challenges in balancing the separation of powers between the branches of government.