The candidates are hard at work this week, practising the art of looking spontaneous, writes Roger Simon at Politico:

“If you were a Martian, you might find it odd that presidential candidates have to rehearse for presidential debates. After all, both Obama and McCain have spent nearly all their adult lives studying serious issues and have spent the past 19 months talking about them on an almost daily basis. But this week, they will stand on mock sets and debate against mock opponents.

“All possible questions and all possible answers (they hope) have been compiled in massive briefing books by their staffs, and the only trick is for the candidates to regurgitate those answers while looking spontaneous and sincere. May the best actor win.”

Read the full story here.