I would be surprised to see this big a defeat unless the turnout in NOVA was severely depressed. I think a 55-44 trouncing is probably what we will see, but if it's high turnout and the Democrats do poorly, they may in trouble there in 2012.
I guess we'll see how Democratic NoVA really is. I don't think it's as Dem as people think. I agree that Fairfax has swung abysmally leftwards at full throttle, but I think Loudoun and Prince William will vote McDonnell as well as Henrico and Abermarle (just four that come to mind).
If McDonnell wins by this margin, there is no mathematical way he can lose these Obama counties.