Looks like I actually did learn something on the way to that PoliSci degree at SDSU.
http://en.wikipedia.org/wiki/Preside...tes#Succession
Under the Constitution, the President serves a four-year term. Amendment XXII (which took effect in 1951 and was first applied to Dwight D. Eisenhower starting in 1953) limits the President to either two four-year terms or a maximum of ten years in office should he have succeeded to the Presidency previously and served less than two years completing his predecessor's term.