The Best Debate Format
The best presidential debate format would have next to no format.
Put the two candidates on a stage. No moderator. No audience.
Between them on a coffee table will be a stack of cards, face down. The cards can be shuffled just after the candidates are introduced. Each card will have an issue that the candidates have agreed is important.
They take turns drawing a card and then discuss the issue for as long as they choose. Discussion done: on to the next card.
When they are done, each can make a six-minute summary statement. They can toss a coin in advance as to the order.
It would be far more revealing than the heavily-structured format.