Final answer:
Congress passed the Twenty-second Amendment to limit presidents to two terms, maintaining the balance of power and democratic principles after FDR's four-term presidency.
Step-by-step explanation:
Congress passed the Twenty-second Amendment to address concerns that arose after President Franklin D. Roosevelt was elected to an unprecedented four terms, breaking the tradition of a two-term limit that was informally established by George Washington. The amendment was ratified in 1951 and restricts a person to two terms as president. This was done to maintain a balance of power and prevent any future president from holding office for an extensive period, which could lead to a concentration of power that might undermine the democratic principles of the United States. The impact of this amendment is evidenced by recent presidents, such as Ronald Reagan, Bill Clinton, and George W. Bush, all of whom were limited to two terms and experienced a loss of political momentum as they became 'lame ducks' towards the end of their second terms.