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.
President of the United States
In response to the unprecedented length of Roosevelt's presidency, the Twenty-second Amendment was adopted in 1951. The amendment bars anyone from being elected president more than twice, or once if that person served more than two years (24 months) of another president's four-year term. Harry S. Truman, president when this term limit came into force, was exempted from its limitations, and briefly sought a second full term—to which he would have otherwise been ineligible for election, as he had been president for more than two years of Roosevelt's fourth term—before he withdrew from the 1952 election.