George Washington
At the end of his second term, Washington retired for personal and political reasons, fatigued and disgusted with personal attacks, and to assure a truly contested presidential election could be held. He did not feel bound to a two-term limit, but his retirement ultimately set precedent. The two-term limit to the presidency was formalized with the 1951 adoption of the Twenty-second Amendment to the United States Constitution. Washington is often credited with setting the principal of a two-term presidency, but it was Thomas Jefferson who first refused to run for a third term on political grounds.
Term limits in the United States
The tradition was challenged by Ulysses Grant in 1880, and by Theodore Roosevelt in 1912. Otherwise no major effort to avoid it took place until 1940 when Franklin Roosevelt explicitly broke it. The 22nd Amendment to the U.S. Constitution was ratified in 1951 formally establishing in law the two-term limit—although it did not apply to the incumbent Harry Truman.