by Anthony G. Greenwald, professor of psychology, University of Washington and Bethany Albertson, assistant professor of political science, University of WashingtonMay 8, 2008 As this year's primaries and caucuses have progressed, we have been analyzing polling data to see if race still plays a role in American politics. Our research suggests that race is, indeed, still a significant factor in determining electoral outcomes, but that it showed up in surprising ways in tallies from some of the states holding Democratic primary elections so far this year (see discussion below). The results of last Tuesday's Indiana and North Carolina open primaries provide further evidence of the effects we observed earlier. The discrepancy between pre-election polls in North Carolina and the actual vote was, given the relative size of the state's black population, almost exactly as we had predicted from the previously observed discrepancies between pre-election polls and actual vote outcomes. Indiana, however, deviated slightly from what our observations of earlier primaries suggested: Clinton received about 7% fewer votes than the analysis had predicted. In other words, strictly on the basis of Indiana's heavily white population, Clinton's margin of victory should have been significantly larger than the two percentage points actually recorded and larger even than the 5-point margin that pre-election polls predicted on average.
Earlier Analysis
The so-called "Bradley effect" was first noticed by survey researchers in 1982 when black Los Angeles Mayor Tom Bradley had a solid lead in the pre-election gubernatorial polls, but lost a close election in California to his Republican opponent. Results from that and other races involving black candidates indicated that, for whatever reason, pre-election polling tended to overstate support for black candidates compared with their actual vote percentages.
Throughout this year's primary season, we have been comparing data from pre-election polls with actual voting patterns as revealed in exit polls to see if the Bradley effect is still operative. In research we jointly undertook last December, we analyzed data from an online test that measures unconscious or automatic preferences2. On the basis of our findings, we surmised that the Bradley effect might well repeat itself in 2008. Our more recent findings, however, suggest a more complicated pattern.
Analysis of primary counts and polling data from the early primaries, including those held before and on Super Tuesday (February 5), indicated that pre-election polls did indeed exaggerate support for Sen. Barack Obama in three states with relatively low black populations -- New Hampshire, California and Massachusetts. But the reverse was true in South Carolina, Alabama and Georgia, where blacks make up a larger bloc of voters.
As shown in the graph, the findings in South Carolina, Alabama and Georgia suggested to us the discovery of a new "reverse" Bradley effect, i.e., that in states with relatively large African American populations, pre-primary polls tended to underestimate support for Obama. (View a larger version of the graph)
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