Actually, Democrats attacked one another and/or Obama when the race tightened in early October. You wouldn't believe the wailing and gnashing of teeth. But seldom would you hear somebody say, well, the polls must be wrong.

The difference is that generally when the polls sour for Dems, they blame themselves collectively. When Repubs see the polls sour, they blame the polls. Neither is objective, but one of them is somewhat less isolated from reality.