Washington - Two senior aides of John McCain told US broadcaster CNN they see "no path to victory" for the Republican presidential candidate as Democratic rival Barack Obama took a commanding lead after Tuesday's vote.

The unnamed aides conceded that with Obama capturing the key swing states of Pennsylvania and Ohio, while holding onto Democratic strongholds like Michigan, there was no realistic means of capturing the White House.

A total of 270 electoral votes is needed to win in the country's state-by-state, winner-takes-all electoral system. The count currently stands at 207-135 in favour of Obama. Winning the reliably Democratic western states California, Oregon and Washington would give Obama electoral votes he needs.

No Republican has ever taken the White House without capturing Ohio's 20 votes. (dpa)