COLUMBUS, United States (AFP) — Donald Trump said Thursday he would accept a “clear” presidential election result but reserved the right to launch a legal challenge, casting the United States into uncharted political waters and his campaign deeper into disarray.

As Trump’s closest allies scrambled to row back debate-stage remarks that called into question the peaceful transfer of power, the 70-year-old populist dangled conditions for his acceptance.

“I will totally accept the results of this great and historic presidential election… if I win,” the Republican nominee told cheering supporters in Delaware, Ohio.

“Of course I will accept a clear election result, but I will also reserve my right to contest and file a legal challenge in the case of a questionable result”.

“I will follow and abide by all of the rules and traditions of all of the many candidates who have come before me,” he added.

The final 2016 presidential debate on Wednesday was dominated by Trump’s refusal to say he would recognize a victory by Democrat Hillary Clinton, 68, who he accuses of conspiring to rig the vote against him.

That stance is unprecedented in modern US political history and has elevated fears of post-election unrest.

Although Trump looks set to lose the election, his campaign sent into a tailspin by a stream of allegations of sexual misconduct, he is likely to garner as many as 50 million votes. 

How his supporters react is now foremost in the minds of officials in the White House and beyond.

It is unclear what impact Trump’s stance will have on the election itself.

“Calling an election rigged doesn’t just undermine foundational democratic norms and principles, it also reduces voter engagement,” said Adam Seth Levine, a professor of government at Cornell University.