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.
Vice President of the United States
The vice president is indirectly elected together with the president to a four-year term of office by the people of the United States through the Electoral College. Section 2 of the Twenty-fifth Amendment, ratified in 1967, created a mechanism for intra-term vice presidential succession, establishing that vice presidential vacancies will be filled by the president and confirmed by both houses of Congress. Previously, whenever a vice president had succeeded to the presidency or had died or resigned from office, the vice presidency remained vacant until the next presidential and vice presidential terms began.