The US opinion-polling industry was one of the winners of this election. The average of the final polls gave Barack Obama a 7.6 percentage-point lead. In the end he won by 5.9 points. So the polls over-estimated his lead by 1.7 points, which means that 0.85 per cent of the vote was put in Mr Obama's column when it actually went to John McCain. That is an error of less than one percentage point: as close to a direct hit as you can get in the imprecise science of social surveys.
The President-elect said in his victory speech, in this election the cynics had their answer. The doubters were confounded. The Bradley Effect, by which voters are supposed to tell pollsters that they will vote for a black candidate but behave differently in the privacy of the secret ballot, turned out not to exist. It was named for Tom Bradley, who lost the California governor's election in 1982, but there has been an increasingly lively debate among psephologists in recent weeks about the quality of evidence for the effect.
In fact, Christopher Carman, a senior lecturer at Strathclyde University, says: "There is evidence that there was something of a Reverse Bradley Effect." He points out that, nationally, only 9 per cent of voters said the race of the candidate was an important factor to them. But in crucial swing states won by Mr Obama, twice as many voters said it was important. In Virginia it was 18 per cent and in Ohio it was 19 per cent, but far from being a negative factor, most of those who said race was important said that they voted for Mr Obama – 63 per cent in Virginia and 54 per cent in Ohio.
The polls also reflected accurately the overwhelming support for Mr Obama among black people. During the campaign, one poll recorded the black vote splitting 96 to 2 per cent in Mr Obama's favour, which some commentators thought was too one-sided. On election day, it was not far off. The figure recorded in the CBS exit poll of 17,800 voters was 95 to 4 per cent. This helped to offset the fact that Mr Obama trailed Mr McCain by 55 to 43 per cent among white voters, who made up three-quarters of the electorate. A two-to-one lead for Mr Obama among Hispanic, Asian and "Other" voters sealed the deal.
The exit poll also confirmed the importance of Mr Obama's grass roots organisation. Nationally, 26 per cent of voters said they had been telephoned or canvassed in person by the Obama campaign, as against 19 per cent who reported contact from the McCain campaign. But in Virginia, 50 per cent said they had been contacted by the Obama campaign and 38 per cent by the McCain campaign.
"The same pattern was repeated in other swing states such as Ohio and Indiana," says Dr Carman. And those voters that had been contacted by a campaign were more likely to end up voting for its candidate.