Writing in The New Yorker, Hendrik Hertzberg novelizes Obama’s race speech into the act that won him the presidency:

In his Philadelphia speech of March 18, 2008, prompted by the firestorm over his former pastor, he treated the American people as adults capable of complex thinking—as his equals, you might say. But what made that speech special, what enabled it to save his candidacy, was its analytic power. It was not defensive. It did not overcompensate. In its combination of objectivity and empathy, it persuaded Americans of all colors that he understood them. In return, they have voted to make him their President.

The reality is far more mundane:

Most voters following the events [the Wright controversy] say they will make no difference in their vote. Seventy percent say the events will make no difference in their vote. Among those who said it would, 14 percent said it makes them more likely to vote for Obama while an equal number said it makes them less likely to support him.

Nearly a quarter of Democrats say the events have made them more likely to back Obama, while a similar number of Republicans say they are now less likely to do so. Three in four independents say the events make no difference, and the remainder are nearly evenly split between those more likely to support him and those less likely to do so.

The speech may have had a small effect on Obama’s poll numbers, but the data aren’t clear. The primary effect of the race speech was that it ended media’s nonstop coverage of the Wright controversy, which might have done significant damage to Obama’s chances of winning the Democratic nomination if it had continued.

Update 11/14 10:12 AM: As Rob reminds us in comments, Wright returned to the news in late April after controversial appearances at the Detroit NAACP and the National Press Club. Obama then disavowed his comments which largely quieted the storm. At that point, however, Obama had what turned out to be an insurmountable lead.