Kerry has made multiple items "the first thing I will do as President." Bush should have the list at the debate and say "When you spoke to X you told them Y would be your first act as President. And when you spoke to A you told them B would be your first act. You have told no less than a dozen groups what your first act would be, but all of them are different. What exactly will be your first act as President?"
Probably Kerry's first act as President would be to give an inaugural address. After finishing it, his second act would be to ask the Secret Service to wake up the other people on the dais.