Imagine him President tweeting classified information. He won't even be able to pretend he didn't know what "C" means on a document.
You did not just go there
Close your eyes. Imagine standing in front of millions in a debate and giving out potential classified information to make a point, imagine sending classified emails to your daughter, imagine getting your server hacked by at least 5 different countries and now subject to blackmail, etc.
You are now Hillary Clinton. Congratulations.