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.
1940 Democratic National Convention
Throughout the winter, spring, and summer of 1940 whether Roosevelt would run again remained unknown. The "two-term" tradition, although not yet enshrined in the U.S. Constitution as the 22nd Amendment, had been established by President George Washington when he refused to run for a third term in 1796, and the tradition was further supported by Thomas Jefferson. Roosevelt, however, refused to give a definitive statement as to his willingness to be a candidate, even indicating to his old friend and political kingmaker James Farley that he would not be a candidate again and that he could seek the nomination; Farley thus began his campaign.