Past voting margins are more reliable than polls based on 1000 voters. So if a state was republican by more than 10% margin, there's no way its going democrat.
Obama to get any state that either Kerry or Gore won easy
Other states that Clinton won and current polls show leaning obama are tossups.
Link to Full SpreadsheetConclusion:
Obama needs one of Virginia, Colorado, Ohio, Florida, Missouri to win.
Best case margin of victory for Obama is 345-189