Focus on the central themes the candidates are using. Don't settle for a one-liner or metaphor to characterize the debate. Look for the surprise comment or unexpected argument. The moment when momentum shifts. Or a gaffe, or misstatement.
Many debates turn on something like that, despite candidates' preparation.
Be prepared to give this special, and thoughtful, treatment in an analysis or commentary. That probably means having someone ready to work on just that. If time permits, or the next day, newspapers can recap the debate, issue by issue, in grid form. Appearance, debate style, confidence ratings, and comments could be added. The number of times each candidate avoided a direct answer.