We've all seen those endless red/blue maps that map the counties in the US by voting percentage favoring Bush or Kerry. Those were very interesting of course, and what we learned is that there is an archipelago of blue islands amongst a sea of red. The map below is different, what it shows is the change in support, by county, for respective Democratic and Republican candidates in the Presidential election. Red counties mark a gain by Kerry, the darker the more pronounced the shift, for Bush the gains are in blue.
This map is unambiguous, the Democrats are poised to make some big gains in the Upper Plains, the Rockies, and much of the West if they can embrace the momentum (which seems to be increasing).
On the other hand, there is a lot of Bush-blue in areas where you wouldn't expect it (mid-Atlantic and lower New England), however, I tend to think (hope) that may have been a temporary effect of Bush capturing the security obsessed undecideds.