There hasn't been. The point was that most of the presidents we've had came from administrative, as opposed to legislative, backgrounds. The administrator (mayor) of a city that is larger than some states would fit the pattern.
“The administrator (mayor) of a city that is larger than some states would fit the pattern.”
I don’t think the mayor will win in the primaries, and if he did, strong conservatives would stay home for the general election, and the Dem would win.