The map above isn't the greatest -- it doesn't, for instance, include Alaska and Hawaii -- but it conveys the point. [Plus, I've yet to see a map on this.] The dark-shaded districts are the ones where Obama or McCain and a Democrat or Republican House candidate, respectively, won the district. In the lightly-shaded districts, McCain and Obama won while a House candidate of the opposite party carried the congressional race. Now, it should be noted that some of the smaller suburban/urban districts don't show up as well as those districts larger in area. However, below you'll see the list of all 83 districts where the vote for president and House were split between the two parties. These seats, or at the very least a fraction of them, are where the battlegrounds will be in next year's midterms.
House seats aside, under the electoral vote allocation system used by Maine and Nebraska, the winner of a congressional district receives one electoral vote and the overall statewide winner wins the two electoral votes that represent a state's two senators. Adding the 56 electoral votes from the 28 states Obama won (plus the three electoral votes from the District of Columbia), the president's electoral vote total would have equaled 301. McCain, meanwhile, would have started off with more electoral votes from congressional districts alone to have suprassed his total under the current electoral college system (173 electoral votes). By adding in the 44 electoral votes for overall statewide victories would have brought the Arizona senator's total to 237 electoral votes.
The bottom line is that the Democrats gained in 2008
[NOTE: I'd like to add a special note of thanks to those who contacted FHQ either via the comments or through email with corrections and/or suggestions. I think we've got it right now. The post is certainly better because of those comments.]
2008 Presidential Primary Calendar
2004 Presidential Primary Calendar
2000 Presidential Primary Calendar