"Old Public Functionary"

That was the sobriquet by which James Buchanan was known when he ran for the U.S. Presidency. He had a lot of executive experience. (Here are charts showing all offices held by our 44 presidents.)

Personally, I think it's hard to beat "The Enchanter" or "The Mistletoe Politician," nicknames for the ever-popular Martin Van Buren.

More nicknames here.