What will happen if Donald Trump challenges the result of the presidential election?
During the third and final presidential debate in Las Vegas Donald Trump refused to say if he would accept the result of the election or not if he loses, sparking concerns about the potential aftermath of the November 8 vote.
"I'll look at it at the time. I'll keep you in suspense," the Republican nominee said when pressed about his claims that the electoral system is "rigged" by Fox News moderator Chris Wallace.
If Hillary Clinton does prove victorious in the election, could Mr Trump challenge the victory and what would happen then?
Can a presidential candidate challenge the result of the election?
If a candidate believes a recount is required they can contest the results of an election.
In 2000, Democratic candidate Al Gore called for a recount in Florida where the result was very close.
Mr Gore appealed to the Supreme Court which ruled that George W Bush had been elected. Mr Gore accepted this decision.
Following Wednesday night's debate, Todd Landman, professor of political science and pro vice chancellor of the faculty of social sciences at the University of Nottingham, criticised Mr Trump for not stating the circumstances in which he would challenge the result.
"What Trump said is, 'I'll decide whether I accept the outcome or not and I will leave you in suspense' - which is quite an arrogant thing to say when it's the highest office of the land that you are seeking," he said.
"It's deeply offensive to a lot of people who support American democracy."
He added: "What he's doing is he is making an unfalsifiable claim, saying 'if she wins the electoral system has been rigged, if I win I beat that rigged system' - and you could never say he was wrong."
What would a challenge by Mr Trump mean for US politics?
If the billionaire businessman were to challenge the outcome of the election, it would make it difficult for Ms Clinton to govern effectively.
Prof Landman warned a possible rejection of the result by Mr Trump would amount to a "failure to uphold a basic democratic principle" and could lead to protests from his supporters.
"Domestically, it would create a lot of instability, a lot of angst, a lot of tension - and America really does need to go through a period of healing," he said.
Prof Landman added that the mobilisation of Trump's supporters into a large-scale movement across the country could prove difficult and would likely be quashed by popular resistance.
Were Mr Trump's comments significant?
Accepting an opponent's victory in the presidential election is a "fundamental principle of modern democracy" in the US, prof Landman said.
"The idea that there is a peaceful transfer of power between civilian elites is a mainstay of American democracy since 1776," he said.
"So to suggest that now - 240 years after our Republic was established - that you would somehow decide whether you accept the result or not is highly problematic from a democratic theory point of view, and it's also highly problematic from a pragmatic point of view."