We can probably assume...that IF the national polls tighten significantly (and to reiterate, the likelihood is that they will NOT), McCain will edge out a victory in North Carolina, Florida, Indiana, North Dakota, Montana, Georgia, and Missouri; put those states in the McCain column for the time being. Likewise, New Mexico, New Hampshire, Minnesota, Michigan, Wisconsin and Iowa all appear safe for Obama, even in the case of significant tightening. Put those in the Obama column.
That leaves our five states in play.
The victory conditions for Obama involving these five states proceed something as follows:
1. Win Pennsylvania and ANY ONE of Colorado, Virginia, Ohio, or Nevada*
2. Win Ohio and EITHER Colorado OR Virginia.
3. Win Colorado AND Virginia AND Nevada.
(* Nevada produces a 269-269 tie, which would probably be resolved for Obama in the House of Representatives.)