Vox's Ezra Klein makes the case. The goals of business and government are not the same. Guess what. Governing is far more complex.
There's a widespread fantasy that some hard-charging CEO could take control of the America government and make it run like a business. But it's mere fantasy: the US government can't run like a business because it isn't structured like a business, it doesn't have the goals of a business, and it doesn't have the tools of a business. It's possible for a brilliant CEO to be a terrible president, and vice versa.
Carly Fiorina's time at HP might tell us a lot about her, but it won't tell us that much about what kind of president she'll be, if only because she'll have to be different as president than she was as CEO.
Perhaps the simplest way to see that is to remember that virtually the entire conversation over Fiorina's tenure at HP is about her acquisition of Compaq; if the US has a bad couple of years, she can't just go buy Canada.