Let’s take a look at Johnson County, Iowa, which Obama won 70-28 in 2008.
That year, by this time, 19,494 people had voted in person, or 21 percent of registered voters.
This year? 17,499, or 19 percent.
So that’s a 2 percent drop in a strong Democrat county. Combine that with a corresponding increase in strong R counties, and increased R participation in early and absentee voting, and you can see why the 2008 D+7 national party ID no longer makes sense.