In the latest round of Hillary versus Donald, the Republican presidential nominee called Hillary Clinton "the devil," referring to her abuse of competitor Bernie Sanders in her race to the top.

At a Pennsylvania rally, Donald Trump made fun of former Democratic contestant Bernie Sanders for capitulating and endorsing Clinton: "He made a deal with the devil."

"She's the devil," he added.

He also told a crowd in Ohio that he feared the US presidential election in November "is going to be rigged."

His comments come after a Wikileaks release revealed Democratic party leaders conspiring to push Sanders out of the race, in order to put their favorite, Hillary Clinton, at the top.

Trump is struggling to save face, after his image took a hit when he made fun of a family who lost a son serving in the US Army.

Trump is currently trailing Clinton 9 points in national polls.