I hope you’re right about Deeds being weak in the Tidewater area, because, as you stated, the RATs can’t win VA without doing well in Tidewater (especially without the huge black turnout from 2008, which will certainly not be replicated this year).
McDonnell should campaign relentlessly in Tidewater, and his supporters should try to sign up as many new voters in the region (and elsewhere of course) as possible in order to maximize this strength. I think Mills Godwin was the last Governor of Virginia from Tidewater (Suffolk I think), but that was back in the late 60’s and early 70’s when the population was only a fraction of what it is now. Deeds is from Bath County, his stronghold is in parts of less populated areas in central, western and northern Virginia.