Very quick observation about Georgia's senate race, which along with California's Proposition 8, may be the thing to watch on Election Night in the event of an Obama blowout. The polls, from what I can tell, are showing a fairly high undecided vote among the African-American population. Rasmussen's most recent poll, which had Saxby Chambliss up by two, shows that 12 percent of black voters are undecided in the senate race. Were those voters to split 4:1 to Jim Martin, that would be worth a net of around 2 points to him, making the race a tie. SurveyUSA, likewise, shows a higher rate of undecideds among black voters (7%) than among whites (3%).
Related thought: it's very difficult to imagine what a Chambliss-Obama voter looks like. It's pretty easy to imagine what a McCain-Martin voter looks like. So if the Georgia polls have Obama down by 4 or 5 points, but Martin down by 2 or 3 points (as they do), something doesn't quite seem right; I'd think the gap should be a bit wider.
Basically, I think this race is a true toss-up rather than a Lean R. African-American voters might be unfamiliar with Jim Martin, who didn't become the nominee until August, but the 'D' beside his name is worth a lot.
Same dynamics may hold to some extent in Roger Wicker's seat in Mississippi, although Wicker is definitely the favorite in that race.