I have thought exactly this. If I ever did run, i would start off by saying, "if elected i would plan to do x, y, z. And just so you know, I will willingly tell you in my younger years i had my fair share of consensual, non-committal intercourse and did drive home from the bars a few times i probably shouldn't have. Previously i have served this country overseas and am proud of my service, now i want to serve my fellow Americans once again."
You don't need a clean background.
You need to be honest and speak about whatever it is that you're ashamed or embarrassed by.
People relate to that
I have thought exactly this. If I ever did run, i would start off by saying, "if elected i would plan to do x, y, z. And just so you know, I will willingly tell you in my younger years i had my fair share of consensual, non-committal intercourse and did drive home from the bars a few times i probably shouldn't have. Previously i have served this country overseas and am proud of my service, now i want to serve my fellow Americans once again."