The nineteenth president of the United States: Rutherford B. Hayes.
The product of one of the most contested presidential elections in the history of the country. (Only in this instance they created a bi-partisan congressional commission rather than conceding to a biased supreme court).
Apparently Mark Twain even stumped for Rutherford. That would have been amazing to see.
Rutherford willingly retired after his first term in office. I can't even imagine a politician doing that nowadays.