I believe tonight is Obama's opportunity to lock this thing up. Debating a man like John McCain, with his experience and knowledge, Obama can hit a home run by demonstrating to the millions watching that he has the judgment and intellectual capacity to grasp and confront the issues of our day, even if he hasn't been around Washington as long as McCain.
For McCain, it will be much more difficult to call tonight a win. He needs to meet the high expectations placed upon him, and hope that Obama blanks on an answer or commits some sort of gaffe. Should McCain trip or fall on any important questions tonight he will lose, assuming Obama gets through in decent fashion.
My prediction? McCain comes out hard and does what we expect him to do, but Obama, despite a rough patch or two, demonstrates that he's been well-prepared and exceeds slightly lower expectations to pull out a win.
The bigger question of course, is will any of it matter?