Far-right groups including the KKK are reportedly threatening to "monitor" voters going to the polls in mostly black neighbourhoods to ensure Hillary Clinton doesn't "steal" the election on 8 November.
Although the Republican Party disassociates itself with such groups, prominent Trump backers are also paying lawyers to monitor the vote and if necessary take legal action against Clinton if she wins.
Many of Trump's more extreme supporters, from the so-called "alt-right", echo Trump's claims that elements in the mainstream media are helping the Clinton campaign and she may "steal" the election.
Meanwhile, some groups such as the vigilante "Oath Keepers" warn Clinton's backers might organise riots, terror attacks or even a war abroad, in order to cancel the elections if it appears that she is losing.
"I seriously doubt any of us are devious enough to even think of the methods that these demon infested parasites can come up with," writes one blogger on The Oath Keepers website.
"What is important to remember is that they are animals; predators; wolves, intent on devouring the sheep and hunting down the sheepdogs. It is also important to remember that cornered animals are the most dangerous."
A member of the "alt-right" website called therightstuff.biz said in an email to Politico that activists would go to polling booths in some black neighbourhoods to "monitor anyone that comes in to vote and make sure that the same people are not voting at multiple locations".
The representative also threatened to depress the minority turnout by "going in to the ghettos in Philly with 40s (beer) and weed to give out to the local residents," reported Vanity Fair. The Nazi Ku Klux Klan is also threatening to "monitor" voting and to mobilise Trump supporters to turn out in force.
Two of Donald Trump's most prominent backers, Roger Stone and Robert Mercer, also claim they will be sending representatives to monitor the vote and if necessary finance legal claims against the Clinton team if she becomes the first woman President.
There is no suggestion that Stone or Mercer are affiliated in any way with the alt-right movement. However the Democratic Party has launched lawsuits against Trump's team in four states - Ohio, Nevada, Pennsylvania and Arizona - to stop his supporters attending polling stations and potentially intimidating voters.
Ohio's Republican Party dismissed the lawsuit as a PR stunt and Stone denies his "Stop the Steal" campaign has direct links with Trump.
"We are not coordinating with the Trump campaign, the Republican National Committee or the individual Republican state committees," said Stone. "We are not engaged in poll watching. We seek only to determine if the election is honestly and fairly conducted."