According to the Bill of Rights Institute, the 22nd Amendment of the U.S. Constitution states that a president is allowed only two terms in office. The amendment relates to the idea of checks and balances and how they help to reduce abuse of power. Checks and balances, states the National Constitution Center, prevent any branch of the government from becoming too powerful.
According to Laws.com, George Washington, on his own accord, decided against running for a third term. He and other founding fathers felt that a two-term limit was appropriate, as they did not want a pseudo-monarchy to occur. Thomas Jefferson added to the rationale of a two-term limit by noting that without a limit, a "President for Life" without constraints was possible, which negated the idea of a democracy.
Laws.com notes that the 22nd Amendment also states that a person who served as acting president for two or more years during someone else's term is not allowed to be elected for more than one term. The original amendment came into effect on March 21, 1947. It was ratified in 1951. The original language stated that the 22nd Amendment was "inoperative" unless it was ratified by three-fourths of the states within a seven-year period from when it was submitted to Congress.