Sometimes I don't really know the purpose of political debates, unless it's to further the agenda of the mainstream media. The narrative is decreed by the networks and moderators, so, the party candidate that they side with gets lowball questions and the opposition gets "gotcha" questions.
Politically we have a few different groups in America. We have libertarians, who are closest in temperment to the true beatnicks of the 50s and the true hippies of the 60s. leave me alone and just be nice. then you have the Independents all of whom actually belong to one main ideology or another, but don't want to be seen embracing any party's complete agenda. but face it, a liberal independent will always vote Democrat etc. There are two groups within the Republican party, the Constitutionalists who believe that the Declaration and Constitution should be the rule of the land, and the Crony capitalist/Hooverites with their populist agenda.
So, it all comes down to knowing what groups the candidates ascribe to and picking the one that is going the way you would support. The important thing for the average voter is that he does enough reading to know the difference between the ideologies.