No offense, but if you've got to go back to Lincoln/Douglas for your most convincing argument for how the United States has a tradition of debate, I think you've lost the argument before you've finished your point.

Nixon/Kennedy, while often represented as a style vs substance debate (it wasn't, Kennedy largely one on both based on broader polling than is generally trotted out, but his good looks to a televised audience certainly helps) is still more than two DECADES before the timetable you're trying to lay out here.