Last night, Barack Obama beat expectations in both Indiana and North Carolina. Let's look carefully at how he managed this feat. We'll begin with Indiana. Let's compare the results from Indiana, Pennsylvania, and Ohio among select demographic groups.

As you can see, Clinton did about as well in Indiana as she did in Pennsylvania and Ohio with white men, white Protestants, and seniors. However, beyond this, she suffered a decline among her best groups. Notice in particular her decline among white women, white Catholics, and union households. Basically, the core of her voting bloc was still with her, but Obama picked off a larger portion of it than he did in Ohio and Pennsylvania.

Why did this happen? It wasn't because of southern Indiana. All of the counties south of metro Indianapolis went for Clinton except Monroe County, where Indiana University is located. Clinton won almost all of these counties in the south by at least 10 points. In some instances, her margins were 30 and even 40 points. All in all, the region bore a resemblance to southern Ohio, where Clinton did really well.

One big problem for Clinton came in metropolitan Indianapolis. Obama beat her in metro Indy by 17 points. Much of this came from Marion County, where a large number of African Americans live. However, discounting Marion County, she only won about 51.6% of the vote. Factor that in with her losses in Fort Wayne, South Bend (home to Notre Dame, and thus a reason why she underperformed among white Catholics), and Gary, and we approach an answer to why the final result was so close.

What about North Carolina? It is instructive, I think, to compare the results from North Carolina to those of Tennessee and Virginia. For the sake of perspective, let's add some basic demographic features of the three states - namely median white income as of 2000 and the percentage of African Americans in the state. We'd expect a priori that as both figures fall, Clinton would do better.

As you can see, North Carolina performed roughly as we might expect, falling in between Virginia and Tennessee. Nevertheless, it is surprising that the results were closer to the Virginia end (i.e. Obama +29) than the Tennessee end (i.e. Clinton +13). What might explain the difference?

Unlike Indiana, it doesn't come from Clinton's core voting group. She did extremely well among white voters in North Carolina. Obviously, she didn't do as well with them as she did in Tennessee. However, she still trounced Obama among white men and white women, regardless of their religious affiliation.

Clinton's problem was with the African American vote, which came in at about 33%. Her trouble in North Carolina, as well as the South in general, is that white voters are more likely to be Republican than in decades past. This has given Obama a demographic edge in the region - one that has actually grown in the past few months. Note that African Americans in North Carolina went for Obama more strongly than they did in either Tennessee or Virginia. In fact, we can see a general trend in the African American vote toward Obama - not just in these states, but nationwide. It has not been much commented upon - most likely because African Americans have been supporting Obama more strongly than any other group. Nevertheless, as time has gone on, the African American vote has clustered around Obama much more tightly.

The following chart has the details. It delineates Obama's margin of victory among African Americans over time. The states are divided into the South and non-South, then arranged chronologically.

We have to be careful not to over-interpret these results because they are relatively small sub-samples of each exit poll. Nevertheless, there is a discernible trend in these numbers toward larger and larger Obama victories. The African American vote now goes much more heavily for Obama than it did at the beginning of the cycle. In fact, if we take Clinton's margin among African Americans in Tennessee and apply it to North Carolina, keeping all else equal, Obama would have barely defeated her.

So, we can conclude that Clinton's narrow victory in Indiana was largely because she didn't do as well with her strong groups as in Ohio and Pennsylvania. However, she did do just as well in the south. It was in metro Indy and in the north that she didn't do as well. On the other hand, Obama's extremely large victory in North Carolina was due to his strength among African Americans, a group with which he has improved over time.

-Jay Cost