Executive experience and presidential candidates

Republican governors who are running for president have made much of the fact that they have had executive experience as governors. They claim such experience prepares them to be president and those candidates without it, like Marco Rubio, thereby are not as qualified. The argument goes only so far, and that's not very far at all.
The principal responsibility of the President of the United States is to be our Commander-in-Chief, to keep us safe. None of the presidential candidates has that experience; not Trump, not Cruz, not Bush, not Kasich, not Christie and not Rubio.