"You have to get everyone you know to the polls. We are going to win. We are going to have one of the greatest victories of all time. This is going to be Brexit times 50," Trump, 70, told cheering supporters in Leesburg, a suburb of Washington DC in Virginia.
His comments came as the pollsters and the media predicted a victory for Democratic nominee Hillary Clinton.
Meanwhile, a woman protester heckled the real estate tycoon with his own vulgar language from an infamous 2005 open-mic recording.
Trump called the protester, a "very obnoxious young lady." who disrupted the speech.