I'd say the most telling thing right now is that McDonnell has dumped the pretense of running a positive campaign and is going 100% on Generic Republican Attack Mode: "THE DEMOCRATS WILL RAISE YOUR TAXES!!!11". If he were really up by 14 like SUSA says, he wouldn't need to be doing that.
Deeds has been running a negative campaign for much of the Summer, which is why he's recovered lost ground. McDonnell has just returned the favor. And as we know, negative adds tend to do better than positive ones, which is why all candidates resort to them at one point or another.