Political public debates don't rely on substance and exact sciences very much, they are socially emotive communications and they tend to use emotional and subconcious communication tricks and tools to achieve the complex influencing effect.
Substance in effect becomes a joke tool, an illusion used in a similar way to hair adverts, used in argument, we become pray to the invention of false proof as it is practiced by lawyers to prove elaborate standpoints which are not motivated by substance but by social gain, and we are forced to hear false notions of substance and to learn to tell apart different types of elaborate deception. fact and evidence becomes a social ceremony and a behaviour pretending to be logically rigorous, with ulterior motives.
It's useful to compare a political debate to a legal debate, which tries to use rigour and proof to advance arguments. Courts and committees are the most rigorous theaters of debate that we have and they are what they are. Their rigor depends a lot on the audience's deduction, as discussed by plato in his treaties on democracy.
Political debates are not based on any exact science so they are communications science rather than actual rational science, they are far away from legal debates and committee debates, and are generally not motivated by rigor but instead by emotional fears and feelings of populations.
it's a topic that takes pages because of it's vague outline. A successful politics debate doesn't necessarily rely on substance very much, it can rely on vagueness to lay doubt on substance of the other, it has as much substance as it has vagueness, and the success of the debate depends more on charisma and the emotive force of the proponents using their conceptual tricks to strike accord.