Id rather have a war time president limited by a rudimentary understanding of economics (McCain) than one limited by a less that rudimentary understanding of the Military (Romney)
I don’t want a president who thinks he’s an economic genius and can micro-manage markets. Usually, folks who claim a subject matter expertise also feel the need display it.
Keep taxes as low as they can be, keep regulations at a minimum, and trust to the collective genius of the markets, is the approach I want, and that doesn’t require a PhD.