Since tonight's debate is a town hall meeting, with supposed undecided voters asking questions, the content is somewhat unpredictable. But my prediction is that McCain will probably take whatever question is asked and turn it into one of the following topics:
Obama's "questionable" associates
Obama's "questionable" judgment
Taxes
Iraq
Terrorism
and if necessary
abortion
This is all McCain has - smear Obama with half-truths or outright falsehoods, accuse him of wanting to raise taxes, insist he is not fit to be commander in chief, and if necessary, accuse him of promoting a "culture of death."
McCain will be provocative and Obama will be cool. McCain will be outrageous and Obama will be dignified.
And if we are really, really lucky, Obama will get in a zinger that will unhinge McCain and get him to show his fangs.