In Colorado, an estimated 56 per cent of eligible voters – some 1.5 million – have cast their ballots by post or in person at early polling locations ahead of the election while in Nevada, almost half of registered voters cast their ballots early.

Democratic Party officials say they are encouraged by early returns which show an apparent advantage for Senator Barack Obama in these and other battleground states including New Mexico, where officials said early ballots were cast in record numbers with over half of eligible voters in some counties predicted to vote before Tuesday.