Lots of people have noted that economic turmoil on Wall Street seems to be throwing John McCain off stride. But there's another half of the equation: falling oil prices. For most of the summer, people equated the bad economy with high gasoline prices. And McCain's solution, while substantively useless in the short run and near-useless in the long run, was simpler and an easier sell.
Now, economic troubles are less likely to be seen as a function of high gas prices and more likely to be associated with wealthy financial interests of the sort McCain wants to shower with hundreds of billions of dollars in tax breaks. That seems like an easier argument for Barack Obama to win.