The basic format of the Lincoln-Douglas debates could still be used today. Since there is no Democrat gentlemanly enough to participate in them, however, the trick would be to get two Republican candidates who would hold small, polite debates designed for substance, not flash.
While many people do not have long attention spans, there are still many that do. Imagine a debate with no moderator, in which two candidates would go into great detail about a subject, say illegal immigration.
The format could be difficult. In each speech, one candidate would speak for 15 minutes, then the other would speak for 15, then the first would again speak for 15 and the second for the final 15.
They would need to give extended background on the subject, possible alternatives being considered, and then state what they prefer the outcome to be.
I like a classic debate—not one of these pop question sound bite photo opts.