Evidence from Gallup's weekly presidential approval results indicates that the racial makeup of its tracking poll changed dramatically between the final week of September and first week of October -- a change that coincides with the beginning of Gallup's reporting of likely voter results in the presidential election.
Although Gallup does not report the racial composition of its tracking poll sample in its weekly presidential approval results, we can estimate the racial makeup of the sample by extrapolating from the reported approval rating of the president among whites, nonwhites and all adults. The estimated nonwhite percentage of the sample for the past five weeks was as follows:
Given the size of Gallup's weekly adult sample, typically over 3500 respondents, the increase from the previous four weeks to the first week of October is very unlikely to be explained by random variation alone. This change, however, does bring the nonwhite share of Gallup's sample much more closely into line with the 2010 Census estimate of the nonwhite share of the U.S. adult population which was 31.8 percent.
In the past, some observers -- including Mark Blumenthal of the Huffpost Pollster -- have criticized Gallup's sampling procedures for under-representing nonwhites in their tracking poll. Assuming that the change seen in the first week of October is permanent and not just a one week aberration, the increase in the percentage of nonwhites in Gallup's latest weekly tracking poll sample is a welcome development that should produce more accurate estimates of not only presidential approval but also support for the presidential candidates among registered and likely voters.