A new survey carried out for the Wall Street Journal and NBC News over the weekend found Clinton on 46 points to Trump's 35.
However, during the head-to-head debate on Sunday the gap between the two candidates grew to 14 points as Clinton surged ahead with a 52 per cent lead over Trump's 38 per cent.
Trump has been embroiled in another scandal since Friday, when a 2005 video obtained by the Washington Post that recorded him talking about groping women without consent was released.
Although he apologised in a 90-second video on Saturday morning, several prominent Republicans (including former secretary of state Condoleeza Rice and Jeb Bush) have publicly criticised him and there has been outcry over his dismissal of the comments as "locker room talk".
British bookies said yesterday her chances had "never looked stronger" to win the race for the White House, as punters poured in bets for the Democrat.