Election 2008: NC's changing electorate working in Obama's favor

Nate Silver at 538.com looks at the latest voter registration numbers in North Carolina, and sees two shifts in the electorate that benefits Democrats. First is party ID:

Since the first of the year, Democrats have added about 250,000 voters to the Republicans' roughly 50,000, while unaffiliated voters also increased their numbers by about 170,000. What was a 10.6 point party ID gap at the start of the year is now 13.0 points. [...]

There is fairly close to a 1:1 correspondence between the party ID gap and the Obama-McCain gap, so these new registrations alone account for about one point's worth of the gains that Obama has made in North Carolina since the summer.

Silver also looks at the changing racial makeup of the electorate. Here's how things have changed:

White share of NC electorate in January 2008: 76.7%
White share as of October 2008: 75.2%
Net change: -1.5%

African-American share of NC electorate as of January 2008: 20.3%
African-American share as of October 2008: 21.4%
Net change: +1.1%

"Other" race* share of NC electorate as of January 2008: 3%
"Other" race share as of October 2008: 3.4%
Net change: +.4%

What does it mean? Silver's analysis:

Assuming that Obama captures 35 percent of white voters, 95 percent of black voters, and 60 percent of "other" voters, the change in the racial composition of the electorate since the first of the year is worth a net of about 1.5 points to Obama in his race against McCain.

Silver is basically right, although the analysis is a bit simplistic. For example, it misses one of the more interesting developments which Facing South reported on last week -- that a big chunk of Obama's increased support in North Carolina seems to be coming from shifting opinion among whites.