Some months ago, few had heard of Mr Obama and most Democrats had assumed that their candidate would be Ms Clinton, while most Republicans had written off Mr McCain. Such are the vagaries of electioneering.
More unexpected swings may be coming. It had initially been assumed that this was an election that the Republicans could not possibly win, so poorly do Americans think of President Bush's handling of the Iraq war and of the economy. That safe assumption can no longer be made, because Senator Obama's skin colour will almost certainly be a polarising factor despite his effort to rise above such divisions. Also, most polls show that in the key battleground states, Mr McCain scores over Mr Obama in the popularity sweepstakes. Also, as someone who is not very well known across the country, Mr Obama runs the risk of his campaign being derailed by unexpected developments like his former pastor's racist comments