I suppose a lot of this is preaching to the choir, but the takeaway from the debates will likely not be the objective content, but rather the independent comparison of how well the candidates did respective to their individual expectations. Waldman writes a good breakdown, with multiple (mostly recent) historical examples.
How to Win a Presidential DebateThe American Prospect
by Paul Waldman, September 16, 2008 (web only)
The first is to understand that the goal is not so much to win the debate but to convince the press that you won the debate. The first step to doing that is to shape their definition of "winning." In the next week and a half, we'll see an absurd amount of discussion about "expectations," as though an election were a round of golf in which everyone is judged according to his or her handicap. Each campaign will come before the press and say with the utmost sincerity that its candidate is a bumbling fool, and it'll be a miracle if he makes it to the lectern without tripping and knocking himself unconscious. The other candidate, each campaign will say of its opponent, is so smart, so prepared, and so skilled that professors of rhetoric everywhere will weep with joy at hearing him bless us with his wisdom and erudition.
You'd think reporters are smart enough not to be swayed by this blizzard of baloney. But you'd be wrong. No one ever played it more shamelessly than George W. Bush's advisers. In 2000, Karen Hughes called Al Gore "the best debater in politics today," which would have seemed absurdly over the top had it not been for Karl Rove, who called Gore "the world's most preeminent debater, a man who is more proficient at hand-to-hand debate combat than anybody the world has ever seen." That's right, the guy who couldn't put away Dan Quayle was supposed to be a better debater "than anybody the world has ever seen." The Bush campaign's efforts were, improbably, entirely successful: Pre-debate coverage that year was driven by the theme of a powerful and confident Gore who would surely crush the tongue-tied and clueless Bush. When Bush held his own, reporters proclaimed him the victor. Four years later, Matthew Dowd, the president's pollster, called John Kerry "the best debater since Cicero."
Of course, making a judgment about who won on the basis of expectations is inherently absurd. If the spread on a Cowboys-Redskins game is Cowboys by 14, and the final score is Cowboys 24, Redskins 20, the story in the next day's paper doesn't read, "Redskins Score Victory by Exceeding Expectations."