The famous “Lincoln — Douglas Debates”
Image found just about everywhere right about now, most notably Crooks and Liars.
To be fair, they did have a lot of debates, Abraham Lincoln and Frederick Douglas.  All very private affairs on matters of policy, and none of them public, as the Stephen Douglas — Abraham Lincoln debates for the Illinois Senate were. I gather Clinton wants her proposed debates to be public, and that the Frederick Douglas — Abraham Lincoln private dialouges would serve no discernable political purpose.