Based on absolutely nothing, this is what I consider the worst case scenario in the Electoral College this November:
Obama 217
McCain 321
In this scenario, of the states John Kerry won in 2004, Obama loses Michigan, New Hampshire, and Pennsylvania, plus one congressional district in Maine. His demands for a rebooting of the auto industry might very well hurt him with auto unions in Detroit; the damage done to Obama by the Clintons could hurt his chances in the Appalachian areas of Pennsylvania; and John McCain's "maverick" status still has potentcy in parts of Maine and libertarian-leaning New Hampshire.
Also in this scenario, McCain is able to keep the Bush red states without much of a problem.