Many in America are bracing for violence and widespread unrest as a chaotic and extraordinary presidential campaign rumbles towards its conclusion.
Increasingly heated rhetoric and political polarisation have been hallmarks of the 2020 presidential election, in a year upended by the COVID-19 crisis and massive demonstrations spurred by the Black Lives Matter movement.
Such is the concern about the potential for civil unrest, authorities have been building a "non-scalable" fence around the White House.
Similarly, businesses in major cities such as New York, Washington, Los Angeles and Chicago have been boarding up their windows in anticipation of riots and looting.
Fuelling this concern, the "Civil War" hashtag has recently been trending on Twitter.
Tom Buchanan, an American living in Australia, says watching the election campaign from afar has been a "really stressful experience".
Owners fit the first floor windows of their Washington D.C. shops with protective wooden panels in case of street riots ahead of the 2020 presidential election. Source: Yegor Aleyev/TASS/Sipa USA
"Everyone is of course watching this, but there is a special horror when you watch your own country falling apart," he told SBS News.
Dr Buchanan, a historian and lecturer at the University of Adelaide, grew up in western Pennsylvania, one of the key battlegrounds of the election.
He said he was "very worried" about violence emerging in the coming days.
"It has all the hallmarks of a situation that you can see in other historical periods where violence has emerged," he said, adding there are "parallels" in the years leading up to the American Civil War.
"For me, the main overarching theme here is that America is slipping out of its democracy, and that has huge implications... violence is part of that. We've already seen evidence of it, and the risks are high in the coming days."
Dr David Smith, from the University of Sydney's United States Studies Centre, said the risk was higher than previous elections.
Supporters applaud President Donald Trump as he speaks at a campaign rally in Goodyear, Arizona. Source: AP
"It's hard to say in absolute terms whether it's high or not. But certainly, the conditions are there that make it more likely this time around than it has been previously," he told SBS News.
The Australian Department of Foreign Affairs and Trade updated its travel advice on 30 October to include the presidential election.
The department's warning against travel was already in place due to the COVID-19 pandemic, but it was updated to warn Australians to "avoid areas where protests are occurring due to the ongoing potential for violence".
'All the hallmarks are there'
In the lead up to the election, some say President Donald Trump has been of discontent in the country by repeatedly making unsubstantiated claims about voter fraud.
At a , he claimed mail-in ballots would contribute to widespread fraud, saying the Democrats are "trying to rig this election because that's the only way they're going to win".
President Donald Trump gestures to supporters after a campaign rally in Goodyear, Arizona. Source: AP
The Brennan Centre for Justice, a public policy institute at New York University, has estimated the risk of mail ballot fraud to be between 0.00004 and 0.0009 per cent.
Ellen Weintraub, the commissioner of the US Federal Election Commission, has .
Mr Trump has also urged his supporters to "be poll watchers" to avoid fraud at voting locations.
"Watch all the thieving and stealing and robbing they do," he told North Carolina rally-goers in September.
This year, the Republicans have sought to recruit up to 50,000 people in 15 key states to serve as poll watchers and challenge the registration of votes they believe are ineligible, according to the New York Times.
Meanwhile, so-called militia groups have reportedly . Professor Buchanan said the development of militias has escalated over the last two decades.
"There are militias on the left and right that are being formed. We've seen, through history, all kinds of situations where militia start off as a form of self-protection, and it escalates from there," he said.
'Massive displays of intimidation'
Last week, a judge in Michigan sided with gun-rights advocates in allowing the open carry of firearms at polling places on election day.
The ruling blocked enforcement of an order by state authorities barring such displays of weapons to prevent voter intimidation.
Professor Smith there have been "massive displays" of intimidation directed at supporters of Democratic candidate Joe Biden.
In one instance, a Biden campaign bus in an apparent attempt to run it off the road.
"These real displays of force and intimidation don't bode well for election day," he said.
Fears about the election outcome are surfacing at a time of increased political polarisation in America, highlighted by clashes during the Black Lives Matter demonstrations as well as large-scale COVID-19 protests.
"If we hadn't had the summer we've had, maybe we wouldn't be thinking this. But there have already been pitched battles between these groups," Professor Buchanan said.
He added partisanship in the US has reached a point where rival sides will "demonise the other".
"The political struggle has become the dominant identity that many Americans have, and that's not normal... we certainly don't have that here (in Australia)," he said.
"There's this sense of 'these aren't our political opponents, these are our enemies'... it doesn't take much for a flashpoint to occur when tensions are this high."
How could this play out?
Back in November 2000, when the vote count for the presidential election was being disputed in Florida, paid Republican operatives descended on polling headquarters demanding that a recount of ballots be stopped.
What became known as the "Brooks Brothers riot" was eventually successful in aborting a recount that Democrats hoped would favour Vice President Al Gore. Instead, challenger George W Bush went on to become president.
Professor Smith said we could see a "much bigger and scarier version" of the Brooks Brothers stunt this year, "which could actually interfere with the vote count itself".
"If rumours start spreading that the election is being 'stolen', that at certain vote counting locations, Democrats are 'producing ballots', then you could definitely see people going and trying to take matters into their own hands," he said.
"That's a very real danger that could lead to violence."
Professor Buchanan has concerns that date back much earlier, when violent civil confrontations erupted in the 1850s in what was then known as Kansas Territory.
Joe Biden speaks at a rally at Franklin Delano Roosevelt Park in Philadelphia. Source: AP
The conflict emerged from debate over whether the territory would allow or prohibit slavery and was characterised by years of electoral fraud, raids, assaults and murders.
"In Kansas, it all came down to one territory. There was one territory that everyone wanted to win, and it evolved into a struggle over the vote, involving militias. There was political violence at the polls," he said.
"It was important because it tipped the balance of the national vote.
"I am hopeful none of this will happen, but we do have to recognise the signs of a democracy that is coming apart."
While many are concerned about the increased potential for violence, Indiana University associate professor Ore Koren said it was still an overall unlikely scenario, because of America's generally strong political institutions.
Of the 12,607 political demonstrations in the US between 24 May and 19 September this year, 95 per cent were peaceful, .
"There were 351 other kinds of incidents, including imposing curfews and perpetrating physical attacks. In 29 of those, there was violence against civilians, where 12 people were killed, nine of them by the police," he wrote.
"And in an additional five drive-by shootings, three police officers were killed by the extremist group the ."
Despite the number of people involved in recent Black Lives Matter and COVID-19 protests, and the fact many were heavily armed, Mr Koren said these casualty figures were "surprisingly low".
Despite concerns Mr Trump has weakened America's political institutions, he said they remain effective in reducing the risk of violence, adding mass political violence usually happens in countries that have no capacity to prevent it.
Professor Smith said the strongest indicator of unrest would be the margin of victory.
"If there is a very clear win for Biden earlier on, there will be less incentive for people to start disputing results. But it is by no means clear that is going to happen," he said.
"And, if Trump pulls out a surprise win, there won't be the same mobilisation for violence on the other side."
Professor Buchanan agreed that a close result would be the most likely to spur violence.
"If it's an isolated incident here and there, the country can get through it. But if it's a very close election, coming down to select states like Pennsylvania, I think we're headed for trouble."
