Recently published and freely available in the online journal Sociological Science:
Simon Cheng and David Weakliem, "Beyond the One-Drop Rule: Views of Obama’s Race and Voting Intention in 2008" [previous versions were entitled "Did America Elect a Black President?"]
ABSTRACT: We use data from a national survey of likely voters conducted before the 2008 election to study the association between Obama’s perceived racial identity and voters’ choices. Voters who saw Obama as biracial were substantially more likely to vote for him, suggesting that many Americans regard a biracial identity more favorably than a black identity. The relationship was stronger among Democrats than among Republicans. The potential implications of our findings for the future of race in American politics are discussed.