BARACK Obama's national poll lead - about 6 per cent in most surveys - is small enough to be blown away by a relatively slight shift in the national mood, but his lead in electoral votes is more impressive, writes Denis Stauntonin Nashville.
US presidents are elected by an electoral college in which each state has the same number of votes as it has members of congress.
Every state has two senators, but sparsely populated states like North Dakota have only one member of the House of Representatives, giving them just three electoral votes. California, the most populous state in the country, has 55 electoral votes.
A candidate needs 270 electoral votes to become president. According to the Real Clear Politics average of polls, Mr Obama is comfortably ahead in enough states to give him 264 votes, compared to Mr McCain's 163, with toss-up states accounting for 111 votes.
If the toss-up states vote according to today's polls, Mr Obama would win by a landslide, sweeping up 364 electoral votes to Mr McCain's 174.
Half of the registered voters surveyed in a CNN/Opinion Research Corp survey this week were asked if Alaska governor Sarah Palin, the Republican vice-presidential nominee, was qualified to be president: 57 per cent said she was not while 43 per cent said she was.
Among the half of registered voters who were asked if Senator Joe Biden, of Delaware, the Democratic vice-presidential nominee, was qualified, 80 per cent said yes and 18 per cent said no.