As we discuss with David Priess of Chatter Podcast (and the author of books on national security and presidential history) - it's tough to run for President when you are the sitting VP. It hasn't worked that often. Just twice since the 12th Amendment changed the election rules surrounding VPs, a vice president has won the big job. David goes into why this worked. And why on many other occasions, it did not work. Learn more about your ad choices. Visit megaphone.fm/adchoices