The U.S. Constitution requires presidents to leave office after a certain period of time, preventing endless control of the executive branch by one person and their party.  In this segment of the How America Elects series, VOA's Jeffrey Young looks at how presidential term limits came about.

Every U.S. president, no matter how popular, no matter how powerful, can win only two four-year terms in office. Then they're out. That was the intention of those who founded the United States, an intention later made part of the U.S. Constitution. 

The U.S. tradition of limiting presidential terms in office goes back to the first president, George Washington, who left office after two terms, for reasons explained by Georgetown University's Mark Rom. "President Washington wanted to avoid the 'cult of personality.'  He also wanted to avoid the transition to a monarchy.  And, if you have a president who can stay in office indefinitely, the fear is that, somehow, this would become a position for life rather than something to serve the public."

Thus began the tradition of presidents serving no more than two terms, something the Founders also saw as a means of stimulating a multi-party political environment. That is, until Ulysses S. Grant, a Republican, won the presidency in 1868 and in 1872.  In 1880, he was not successful.

The next time a president sought a third term was in 1912.  Republican Theodore Roosevelt, who served from 1901 to 1909, abandoned his party and formed a new one, the Progressive Party, to challenge the Republican nominee, William Howard Taft.  Roosevelt defeated Taft, but he did not defeat Democrat Woodrow Wilson, who went to the White House.

The only U.S. president elected to more than two terms was Democrat Franklin D. Roosevelt.  In 1940, after Roosevelt already had served twice as president.  World War Two was savagely underway in Europe and Asia.  Roosevelt ran for and won a third, and then, a fourth term. 

The feelings of the electorate at that time are described by Howard University's Lorenzo Morris. "The simplest answer, I think, is that Americans recognize that, under stress, as any country would, and it's probably the only law of politics, [that] under stress, countries tend to re-elect the leader, tend to go focus on the leader."

Then in 1946, the Republican Party took control of Capitol Hill and passed a constitutional amendment that limits presidents to two full terms. Georgetown University's Mark Rom explains Congress' motivation to take action. "The Republicans were concerned that a four-term liberal president was not to their liking, and to keep a long parade of liberal presidents from coming into office, [they passed an amendment that would set up the rule] 'two terms and you're out.' "

The 22nd Amendment to the U.S. Constitution was ratified by the states by 1951. Presidents can win two full four-year terms, and can also serve for less than half of another term if the previous president dies or otherwise leaves office.  While some have called for its repeal, others say this amendment is what the Founders intended to ensure a vibrant democracy.