The economy has been the most important issue since March, and the events of the past week have only magnified its importance. Still, it's important to remember that the president has a limited amount of influence when it comes to economic policy. The executive's actions are obviously important (e.g. Treasury Secretary Henry Paulson's recent prominence), but the Congress still has the final say in fiscal matters, and the Fed has almost complete control over monetary policy.
George Mason professor Tyler Cowen has an excellent description of how presidential elections relate to economic policy in this NY Times article.