In another national survey (Internet) just after the election itself, Sniderman and Stiglitz (2008) thoroughly explore racial prejudice and 2008 vote choice. They find that American voters do not hesitate “to make frankly derogatory comments about blacks.” For example, about one out of five whites surveyed described “most blacks” as “violent”; essentially the same fraction also described them as “boastful”; almost one out of three said they were “complaining.” Overall, the investigators ranked 10% of respondents as high scorers on a prejudice index (built from five items). Among Republicans, variation in this prejudice index does not significantly relate to declared votes for Obama. However, among Democrats, the effect is significant and strong; for those in the bottom third on the prejudice index, 95% voted Obama; but for those in the top third the percent drops to 62, for a difference of minus 33 points. This large defection appears partially offset by voters who view blacks with “esteem.” Considering those in the bottom third on this esteem index, 77% voted Obama; but for those in the top third the percentage rises to 96, for a difference of +19 points. (Relatedly, Craemer et al.  report that some white voters may have come to a psychological closeness to Obama, enabling them to vote for him.)
Using these above differences, as reported in Sniderman and Stiglitz (2008), we go on to take the positive esteem number (+19) from the negative prejudice number (−33), implying a 14-point loss among Democrats. While that calculation suggests to us a substantial racial cost, translation of that number into a precise vote estimate remains uncertain, and the authors themselves do not offer any such calculation. However, that task is carried out by Aistrup, Kisangani, and Piri (2009) in their analysis of a pre-convention survey from the South. In a logistic regression model, with the dependent variable vote intention for McCain or Obama, and under extensive controls (e.g., ideology, party identification, SES), they find racial resentment has a strong impact. For example, among Democrats, when the race resentment index shifts upward one standard deviation, the probability of a McCain vote increases from about 40% to 58%. Unfortunately for our purposes, this survey confines itself to one part of the country.-Lewis-Beck, Michael S, Charles Tien, and Richard Nadeau. "Obama's Missed Landslide: A Racial Cost?" in PS: Political Science and Politics, Vol. 43. No. 1 (published online January 15, 2010).