On The Gist, Jonathan Prince has helped candidates such as Bill Clinton and John Edwards prep for high-stakes debates. Now, he’s got some advice for Hillary Clinton as she faces round No. 3 with the most unpredictable candidate of the modern era. Prince has worked for the Clinton and Obama administrations, but now he’s the head of communications for Spotify. For the Spiel, how do you rig the most well-observed election on Earth? The answer is: You don’t.Today’s sponsors: Squarespace. Start your free trial today at Squarespace.com and enter offer code gist to get 10 percent off your first purchase. And by Betterment, the largest automated investing service. Get up to six months of investing FREE when you go to Betterment.com/gist.  Join Slate Plus! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today at slate.com/gistplus.Learn more about your ad choices. Visit megaphone.fm/adchoices