What role did race play in Obama’s loss?

The debate over whether the reluctance of white voters to support a black candidate once in the privacy of the voting booth is what explains Obama’s loss is raging here in New Hampshire. First Read lays out the case,

“we can only think of three races in which the public polls and the final result were SO off, and they all involved African-American candidates: Bradley’s ’82 gubernatorial campaign in California, Doug Wilder’s surprisingly narrow ’89 victory for Virginia governor, and Harvey Gantt’s surprise loss for North Carolina Senate. There is no poll question we can find that can truly measure this phenomenon. But African-Americans are thinking this, and the difference between Iowa and New Hampshire is a voting curtain: Democrats didn’t have one in Iowa; they had one in New Hampshire.”