Final answer:
The 22nd Amendment was enacted in 1951 following Franklin D. Roosevelt's four-term presidency, which lasted a total of 16 years. It limits presidents to serving no more than two terms.
Step-by-step explanation:
Franklin Delano Roosevelt (FDR), the 32nd American president, served an unprecedented four terms in office, which is a total of 16 years. This occurred during a critical period in American history marked by the Great Depression and World War II. As a result of FDR's lengthy presidency, Congress passed the 22nd Amendment in 1951, which imposed a limit of two terms for future presidents.
The enactment of the 22nd Amendment was a significant moment in the realm of presidential powers, as it solidified the unwritten rule set by George Washington into a constitutional mandate. The amendment stated that no person could be elected president more than twice, and anyone who serves as president or acting president for more than two years of a term to which someone else was elected can only be elected once.
Despite the restrictions placed by the 22nd Amendment, subsequent presidents have continued to exert significant influence. Presidents like Ronald Reagan, Bill Clinton, and George W. Bush each served the maximum eight years permitted, often becoming "lame ducks" toward the end of their second terms as focus shifted to their potential successors.