With the emergence of candidates with non-political backgrounds in the 2016 election such as Donald Trump, Carly Fiorina, and Ben Carson, will one of these candidates' possible election be unprecedented?
Ronald Reagan comes to mind with an acting background, but I'm looking at no political background whatsoever; Ronald Reagan was the Governor of California prior to becoming president.
Yes, but they call came straight from the military. Zachary Taylor considered himself an independent and had never voted before the year he got elected. Ulysses S Grant entered the campaign as the Commanding General, although he had previously been Secretary of War. After WW2, Eisenhower was President of Columbia University and was involved with the Council on Foreign Relations which was kind of a political training ground for him. He moved back temporarily to be Supreme Commander of NATO in Europe before he was elected president.
But in terms of coming straight from business with no public office or military service, no, they would be unprecedented. Everyone else has previously held a high-ranking office in either the military or federal/state government.