The 25th Amendment to the US Constitution is often mentioned during moments of political crisis, but few Americans fully understand what it actually does, how it works, or how rarely it has been used in modern history.

In recent years, the amendment has repeatedly resurfaced in conversations surrounding Donald Trump, particularly during periods of controversy, public concern over leadership stability, or questions about a president’s ability to govern.

Ratified in 1967 following the assassination of John F. Kennedy, the 25th Amendment was designed to clarify what happens if a president dies, resigns, becomes incapacitated, or is deemed unable to perform the duties of the office.

Before its adoption, the Constitution offered little guidance on presidential incapacity, leaving dangerous gray areas during moments of national emergency.

The amendment contains four sections, but it is Section 4 that has drawn the most attention in modern political debates.

Section 4 allows the vice president and a majority of the president’s Cabinet to declare that the president is “unable to discharge the powers and duties of his office.” If invoked, the vice president immediately becomes acting president.