May 06, 2008

Vote by Race in NC and IN

I thought it might be helpful, given our focus on the racial composition in the electorates for Indiana and especially North Carolina, to post a summary of results by race in each state. Fortunately, just about all of the pollsters have released results by race on their final polls. A summary of each follows.

Let's start with North Carolina, where the ultimate margin will be extremely sensitive to the racial composition, as these numbers will make clear.

Most of the surveys have had the Clinton percentage of the white vote at roughly 61%, and -- with one notetable exception -- at about the average of 10% of the black vote. Much of the variation in the overall margin comes from the percentage of African Americans in the full sample. Most of the pollster have been reporting an African-American percentage of 32% to 33%. But as FiveThirtyEight's Poblano points out about his very helpful North Carolina prediction spreadsheet,

[A]n increase of 1 percent in the fraction of the electorate that is African-American translates to roughly a 1-point increase in Barack Obama's margin over Hillary Clinton. So -- if the pollsters are assuming 33% black turnout when it will actually be 40%, that would add 7 points to Obama's margin -- putting us in the 13-14 point range.

In the same post, Poblano makes the case that the African American percentage in North Carolina is likely to be higher than the 32% reported by most pollsters.

Another huge issue in trying to use these findings as the basis for vote projections is deciding what to do about undecided voters. In South Carolina pre-election polls vastly underestimated Barack Obama's vote, mostly among African-Americans. Polls conducted with an automated methodology in South Carolina showed Obama doing better among black voters than those using live interviewers, and PPP's Tom Jensen and FiveThirtyEight's Poblano 'have both noted that (as Poblano put it) "polls have significantly underestimated Barack Obama's margin of victory in Southern states with substantial black populations." This pattern in past primaries argues for assuming that Obama's support among African-Americans will be higher tonight than the 82% average noted above.

On the other hand, TNR's Noam Scheiber noticed that Clinton does slightly better among IVR pollsters in North Carolina, and he wonders if the automated surveys are "picking up on a queasiness [about Obama and Wright that] black voters are less comfortable sharing with human interviewers." Perhaps, but notice that much of the difference comes from the InsiderAdvantage poll.

What's your guess? You can plug numbers into Poblano's spreadsheet to test your theories.

The most consistent aspect of the Indiana results is Obama's percentage among white voters, which nearly every pollster pegs at or near the average of 39%. If Clinton gets 60% or more of the white vote tonight, the only question will be the size of her margin given the percentage of African-Americans. To win, Obama will need to hold Clinton a few points under 60 and boost the African American share to roughly 15%.

One striking inconsistency in Indiana is the result among African-Americans. However, we should keep in mind that the sample sizes are usually very small (probably in the range of 50 to 100 interviews), so we should not be surprised to see big variation. Moreover, the pattern is not consistent across pollsters by mode.

Update: I neglected to include explicit links above, but I did posts yesterday on what the composition by all of the North Carolina and Indiana polls by race and other demographics.

-- Mark Blumenthal

May 06, 2008 in The 2008 Race

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