Final answer:
Before the 22nd Amendment was ratified in 1951, the president could be reelected indefinitely. It was Franklin Delano Roosevelt's election to four terms that prompted the introduction of this amendment, which now limits the president to two four-year terms.
Step-by-step explanation:
Originally, there was no constitutional limit on the number of terms a president could serve. The precedent of serving only two terms was set by George Washington. It wasn't until after Franklin Delano Roosevelt (FDR) was elected to four terms that the 22nd Amendment was ratified in 1951, which now limits a president to two elected four-year terms.
Therefore, the president was to serve a four-year term, which could be renewed indefinitely prior to the enactment of the 22nd Amendment. After the amendment, the limit was set at serving no more than two four-year terms.