Angry protests, acts of violence and now a targeted attack involving explosives — it seems America is more politically and socially divided than ever.
Over the past few years, leading up to and after the Presidential Election in 2016, researchers have been measuring sentiment across the party divide.
The results are increasingly alarming.
Left and right have never been further apart and the moderate centre is rapidly evaporating, as is the willingness of people to listen to — or even associate with — their political opposites.
Liberals and conservatives don't just disagree, but increasingly refuse to live near, work with, or socialise with each other.
And according to a recent poll, one third of Americans strongly believe a civil war is inevitable.
During a rally of his supporters on Thursday, US President Donald Trump called for calm in the wake of several pipe bombs being sent to high-profile Democrats, including Barack Obama, Joe Biden and Bill and Hillary Clinton. News organisation CNN was also a target.
"There is one way to settle our disagreements — it's called peacefully, at the ballot box," Trump told the crowd.
A dangerous new low
A number of crude but functional pipe bombs were mailed to high-profile targets across the United States yesterday, sparking mass evacuations and putting security agencies on high alert.
Among the recipients were former President Bill Clinton and his wife, former Secretary of State and presidential nominee Hillary Clinton, former President Barack Obama, and Democratic politicians Maxine Waters and Debbie Wasserman Schultz.
But after three years of hyper-partisan, divisive and at times violent rhetoric from the leader of the free world, is his sudden call for unity too little, too late?
Fresh reports indicate authorities intercepted an explosive addressed to former Vice President Joe Biden.
Former CIA director John Brennan and the New York bureau of news network CNN were also targeted.
New York City Mayor Bill de Blasio described the threats as an act of domestic terrorism and sparked a war of words over who is to blame.
US political expert, author and host of ABC's Planet America John Barron said the apparent co-ordinated plot was deeply concerning.
"In the 1990s when a couple of white extremists targeted the Federal Building in Oklahoma City, it was very much read as being in response to the hyper-partisan environment that had been drummed up by certain Republicans," Mr Barron said.
"President Clinton at the time was able to skilfully call for an end to that partisan rancour, saying that this is what it leads to — you reap the hatred you sow.
"The difference here is President Trump is the sower in chief. He's been exploiting deep partisan, gender and ethnic divisions in the United States for the past three years."
All of the targets have one thing in common, Barron said — they have all been criticised repeatedly, and often pointedly, by Trump.
"In the same speech today where he was calling for unity, peace, love and understanding, his supporters in the crowd were still chanting 'lock her up!' about Hillary Clinton, whose just had a pipe bomb mailed to her," he said.
"He blamed the negativity of the media. For him to attack the media at a time when CNN was evacuated because of a pipe bomb in their basement is pretty remarkable.
"It's not even dog-whistling — it's a full-throated wolf bark to the most conservative and racist elements in America."
Trump has repeatedly described sections of the American press as "the enemy of the people" and has focused his attacks on CNN in particular.
Shaun Ratcliff from the United States Studies Centre at the University of Sydney said certain hard line commentators today were insisting the attack was a "false flag" orchestrated by Democrats to win sympathy.
"I'm sure some people do believe that. There are some people who won't accept that their side is ever wrong. I don't know how prevalent those views are," Dr Ratcliff said.
Ironically, it is some of those very voices who could be blamed for whipping up hysteria to the point of violence, he said.
"Some of the rhetoric that certain political activists have been using in recent years could be seen as helping to increase the chances of things like this happening."
A people divided
Research by the Pew Research Centre in 2017 found the partisan divide over political issues related to race, immigration and welfare has widened significantly.
On average, there was a 36 per cent different of opinion across party lines, up from just 15 per cent in 1994.
It seems Americans are moving further and further to the extreme ends of their respective ideologies, away from the moderate centre.
In fact, a study by Michigan State University associate professor of psychology and global urban studies Zachary Neal, found the divide between Republicans and Democrats is the worst it has ever been.
"What I've found is that polarisation has been steadily getting worse since the early 1970s," Prof Neal said.
"Today, we've hit the ceiling on polarisation. At these levels, it will be difficult to make any progress on social or economic policies."
It's a fear shared by many academics. How can any meaningful reform be achieved when people are so far apart?
John Hopkins University professor of history Louis Galambos believes America's worsening differences of opinion has all but torn the nation apart.
"Our nation has been ripped apart by political discord, ad hominem attacks and deep rifts between the dominant political parties," Prof Galambos said.
The feeling of damaging division is not exclusive to academics and pollsters.
A study by Rasmussen Polling in July found 55 per cent of people feel the country is less united than ever and 13 per cent had ended a friendship over political issues.
Unlike any time in modern history, people are choosing their views over interpersonal relationships.
Analysis by Scientific American magazine reported that people on the left and right are "increasingly unwilling" to live near, work alongside or socialise with each other.
"If Americans slide into seeing all policy debates as battles between 'us versus them', we stop selecting policies based on their actual content," the report said.
While The Brookings Institute public policy expert Jonathan Rauch said America is at risk of becoming two countries living side-by-side but not together.
"Political segregation may be on the rise. Like-minded people may be clustering together socially or geographically, so that fewer people are exposed to other points of view," Mr Rauch said.
Social media only making that segregation worse, as people curate their own digital circles and almost blinker themselves to differing opinions.
In a piece for the San Francisco Chronicle, political commentator Victor Davis Hanson wrote that the speed of the internet is the "enemy of common sense and restraint".
The internet and social media often descend into an electronic lynch mob," Davis Hanson wrote.
"In a nanosecond, an insignificant local news story goes viral. Immediately hundreds of millions of people use it to drum up the evils or virtues of either progressivism or conservatism.
Every day we will either treat each other as fellow Americans, with far more uniting than dividing us, or we will continue on the present path that eventually ends in something like a hate-filled Iraq, Rwanda or the Balkans.
A palpable anger
Rather than agree to disagree, a large number of Americans are increasingly unwilling to even debate, Frank Mols from the University of Queensland's School of Political Sciences and International Studies said.
"A lot of Americans are caught up in a kind of tribal fight," Mols said.
"We are social beings as humans who want to belong to a group and want cohesion, but once the tribal switch is triggered, we view the world as 'us versus them'. I think we're seeing that with a high percentage of Americans."
A big part of the problem lies in what Mols describes "the outcry paradox" where both sides make the sense of anger worse by reacting to everything.
Extreme reactions are occurring on the fringes of both sides, and it's bleeding into the more centrist populations on the left and the right.
"People who are upset constantly seem to engage in outcry, and that outcry comes with emotion that easily boil over and lead to overstepping certain boundaries," Mols said.
"All that does is alienate your opponent, so to speak.
"A massive body of literature will tell you that persuasion comes from empathy and shared social experience. You can see why both sides are divided — they've forgotten that.
"Blowing the opposing party away with anger or rage is not the way to unity. It's empathy, engagement, respect and finding common ground."
The next civil war
As Americans become more divided, research shows they are also losing faith in the institution of government and politics at an alarming pace.
Research by the United States Studies Centre found that Republicans have lost the most trust, even though their party controls the House, the Senate and the White House.
Alarmingly, the Rasmussen Polling research found 31 per cent of Americans believe a second Civil War is inevitable and will break out within the next five years.
"I'm not surprised at all," Mols said.
"I don't want to exaggerate it. It's easy to fear the worst and be alarmed. We need to be careful with that. But it's something that worries people."
He believes a lowering in the standard of the presidency has created a "normalisation" of aggression and difference.
"Whether you like Trump or not, I think it's something we can easily ascertain — the way the leader is conducting himself is quite unique," Mols said.
"There are many occasions in which Trump has openly glorified or encouraged violence. There is footage of him at countless rallies talking about violence in a positive way.
"Rhetorical or joking or whatever, that has an impact and it's quite chilling. I think it has led to changes on the ground."
The polarisation we are seeing goes back to the 1960s, Ratcliff said, and has been progressively getting worse since then.
But in recent decades, it has escalated — Republicans are getting more conservative and Democrats are becoming more progressive.
"It makes coming together and finding common ground increasingly difficult, particularly for the politically engaged.
"The rhetoric is quite divisive at the moment."
However, he does not believe America is on the brink of destruction or a new kind of Civil War by any means.
Nor does Barron, although he concedes that the breakdown of the middle political ground has seen left and right pushed to their extremes.
"There is a massive divide along racial and economic lines, clearly fuelling the right nationalism that has helped Trump's candidacy and presidency," he said.
American history is littered with examples of deep political and social division, he said. The past four decades have been punctuated by periods of upheaval on various partisan issues.
"But there is no issue to have a civil war over. It's hard to imagine it happening but you can certainly see that increasing Americans are divided. It's not great for national unity."
Trump's impossible task
However, he also pointed the blame at the press, politics and protesters, which left some critics disappointed.
"Those engaged in the political arena must stop treating political opponents as being morally defective. The language of moral condemnation … these are arguments and disagreements that have to stop," Trump said.
"No one should carelessly compare political opponents to historical villains. It's got to stop. We should not mob people in public spaces or destroy public property.
"The media also has a responsibility to set a civil tone and stop the endless hostility and constant negative and oftentimes false attacks."
The way to settle political difference, as it had always been, was at the ballot box, he added.
However, seemingly tongue-in-cheek, he added that: "If you're going to vote Democrat, don't bother."
Is America broken?
While the view of the US — particularly from outside — is concerning, Ratcliff isn't convinced it's representative of most Americans.
"I believe most of America is purple — it's not purely red or purely blue," he said.
"I want to make the point though that we see on TV, the anger about politics, doesn't necessarily represent every American. Most people are still near the centre, I think."
But where is the country heading from here?
While the worst of both sides of politics are amplified, Mols is hopeful "decency will prevail" and a return to something resembling the norm will occur.
But that will require some quiet calm, and he's not sure how America gets there.
"Most Americans are still the silent, normal majority, I believe. We talk about the extremes on both sides but perhaps not the vast majority."
Barron said much will hinge on the midterm elections in November, when the Democrats hope to take back control of the House.
What that will allow is for a raft of special investigations of Trump, his Administration and other controversial issues including Russia's alleged interference in the election.
"It will mean a hyper-partisan atmosphere, a lot of scandals swirling around the Trump administration and another two years just like the past two years but probably worse," he said.
"And probably the day after the midterm elections, we'll have 20 Democrats announcing they're running for president. We're off to the races again for a two-year campaign.
"It's going to be a fascinating period but it's not going to settle down. There will be nothing normal about American politics for a long, long time."