The market actually hasn't reacted that badly to Lehman Brothers. At this writing, the Dow is down 281, although that number could just as easily be 60 or 600 by the time you read this.
People nevertheless seem to think that this will be some sort of linchpin event in the campaign. I don't necessarily buy that, because I think that most voters grasp intuitively that markets are markets, and that policymakers have less to do with their direction than they might with something like job creation.
To the extent there are opportunities, however, you'd think they'd favor Obama. He should have the much easier time of things, because people naturally associate Wall Street with the Republicans, and because he can simply link the troubles to the failures of the status quo under George W. Bush.
McCain, by contrast, is under more pressure to actually propose solutions, which is difficult because there aren't a lot of good ones here. He certainly needs to improve his messaging over where it was in his morning appearance in Jacksonville today, where he was borderline incoherent on the subject of the financial crisis.