In his eyes, the world is an unforgiving place where cities are "war zones," where "rapists" are streaming across the border and where jealous rivals are hatching plots to humiliate America and Trump personally.
To prevail in such an environment, he suggests, the response to any slight must be swift and overwhelming. Dwelling on limits imposed by law or tradition is usually a secondary concern.
This framework has expressed itself in policy, in which Trump has extolled the use of torture, threatened reprisals against the families of terrorists and pledged to jail Clinton, a former senator and secretary of state. It has expressed itself rhetorically in vicious insults against critics and in his encouragement of violence by supporters.
"She's nasty, but I can be nastier than she ever can be," Trump told The New York Times after Clinton criticized his past comments on women's appearances in their first debate. The next day, he suggested at a rally that she had cheated on her husband, while offering no evidence for the claim.
It has expressed itself in the video of Trump boasting about sexual assault and demeaning a journalist who he said refused his advances. In recent days, he's threatened to sue women who have publicly accused him of unwanted sexual contact and to break up large companies (including Comcast, which owns NBC News) that produce media coverage he finds unfair.
It has also expressed itself at Trump's rallies, where supporters have reflected the candidate's harsh tone.
"We're all Second Amendment pros, we want our country back like he just said, and she's not going to give it to us," a Trump voter, Tammy Wilson, said at a Florida rally this month after predicting people would "rise up" if Trump loses.
The Trump campaign did not respond to requests for comment for this story. With Trump's language heating up in the final days and his list of enemies growing fast, some civil rights groups and law enforcement officials are raising fears that things could get out of hand.
"We are concerned about the possibility of violence on Election Day and afterwards," Heidi Beirich of the Southern Poverty Law Center told NBC News.
Code of vengeance
A strict code of vengeance seems to be a point of pride for Trump, who has touted his philosophy on numerous occasions.
"What happens is they hit me and I hit them back harder and, usually in all cases, they do it first," Trump told Fox News in April. "But they hit me and I hit them back harder and they disappear. That's what we want to lead the country."
The same month, Trump told a radio host that the Bible verse that's influenced him most is "an eye for an eye."
"They laugh at our face, and they're taking our jobs, they're taking our money, they're taking the health of our country," Trump said in explaining his affection for the passage. "We have to be firm and have to be very strong. And we can learn a lot from the Bible, that I can tell you."
He's explained his support for torture and war crimes as a case of having "to fight fire with fire." He's justified an abusive tweet mocking Texas Sen. Ted Cruz's wife, Heidi, as an example of "counterpunching," one of his favorite phrases.
"Am I not allowed to respond?" he asked after being criticized for feuding with a Gold Star family that denounced his proposed ban on Muslims.
"I know of no presidential candidate and no president who has used that kind of imagery on a repeated basis throughout an entire campaign," Martin Medhurst, a professor at Baylor University who specializes in political rhetoric, said. "There's simply nothing like it."
Violence as policy
At the second presidential debate, in St. Louis, millions of viewers waited to hear how Trump would respond to the newly released 2005 Access Hollywood tape in which he boasted of grabbing women's genitals.
When asked whether his comments constituted sexual assault, the candidate briefly apologized and dismissed the remarks as "locker room talk." But then his answer took an abrupt turn for the bloody.
"You know, when we have a world where you have ISIS chopping off heads, where you have them, frankly, drowning people in steel cages, where you have wars and horrible, horrible sights all over and you have so many bad things happening, this is like medieval times," Trump said. "We haven't seen anything like this."
It was a revealing riff, one that Trump has used many times before, and makes sense in his confrontational worldview: as long as an enemy somewhere is engaged in bad behavior, there's little point fretting about the goodness of one's own.
In the case of the debate, Trump brought up ISIS when talking about his own personal conduct. Usually, though, he's brought up the same descriptions of executions while rousing audiences with talk of war crimes.
"The enemy is cutting off the heads of Christians and drowning them in cages, and yet we are too politically correct to respond in kind," he wrote in a letter to USA Today in February explaining his support for torture.
"We have to fight so viciously and violently because we're dealing with violent people," he said in a June speech endorsing waterboarding that also referenced ISIS executions.
Trump has made this willingness to out-brutalize opponents a central point of his political message. It was an effective strategy during the Republican primary campaign, when his rivals were largely uncomfortable straying from constitutional limits or traditional assumptions of human decency.
On the eve of the New Hampshire primary last February, for example, Trump repeated the words of a supporter who called a leading opponent, Ted Cruz, a "p***y" for not showing enough enthusiasm for torture.
Trump later credited the moment with helping power him to victory in the state. "Torture works, OK folks?" he said later that month. "If it doesn't work, they deserve it anyway," he has also said.
Officials who served under the last Republican president, George W. Bush, engaged in heated debates over issues like torture that tested legal boundaries. Bush ultimately authorized the use of waterboarding, arguing it did not rise to the level of torture. Congress eventually outlawed the practice.
It's notable, however, that some of the most prominent figures on both sides of those Bush-era arguments are now among Trump's fiercest critics.
"On issue after issue, Trump lacks a fundamental humanity in his approach to people that is absolutely startling," said Alberto Mora, the former top Navy lawyer who led efforts to oppose practices like waterboarding within the Bush administration. "His support of torture is of a piece with his innate cruelty."
John Yoo, author of the so-called "torture memos" that provided legal footing for enhanced interrogation techniques like waterboarding, condemned Trump using equally strong language, even comparing him to fascist dictator Benito Mussolini.
"He's the classic demagogue described well in the Federalist Papers that our system is designed to stop," Yoo said.
For Mora and Yoo the issue isn't just the proposals Trump has championed, but the underlying philosophy that they see behind them.
"He's pandering to the sort of visceral reaction people have for revenge against terrorists, which is not what motivated the Bush administration," Yoo said.
Trump's public remarks often suggest that brutal adversaries should set the terms of engagement.
"Look, you have to play the game the way they're playing the game," Trump said on CBS in March, when asked whether he was stooping to the same level as the "savages" he sought to defeat.
In a GOP debate last December, when criticized for his plan to "take out" the civilian families of terrorists, Trump asked: "So they can kill us, but we can't kill them?"
Army Lt. General Keith Kellogg, an adviser to Trump, told NBC News that the candidate would uphold American law and international treaties such as the Geneva Convention that the candidate has criticized on the trail.
"His point is that he will do everything he can to protect the American people, everything, but he also understands there are certain rules," Kellogg said.
Trump himself has said as much after initially suggesting at a debate he would override military officers who refused to carry out illegal orders. He currently enjoys support from a number of retired military leaders. Yet, dozens of senior Republican national security officials in August signed onto a letter opposing his candidacy. In March, 122 prominent foreign policy and national security conservatives also warned of Trump's "embrace of the expansive use of torture."
"I would never trust him to follow the law," said Eliot A. Cohen, a former State Department official under Bush who helped organize the March statement. "We're dealing with a dangerous egomaniac who has no control of himself, recognizes no limits, no bounds and does not recognize the constraints of law or anything else."
Telling it like it is
Waiting in line with thousands of Trump fans outside the Mohegan Sun Arena in Wilkes-Barre on October 10, some of the nominee's supporters offered a different take on Trump's tough stance on security.
To Ben Johnson, a retired firefighter wearing a "Deplorable Me" T-shirt and a "Make America Great Again" cap, the problem isn't Trump, it's everyone else. Other politicians, Johnson said, offer a "rosy picture" of the world. Trump, he said, is a realist, especially on issues like terrorism.
"I dug at the World Trade Center for two weeks, so I saw what these people are capable of up close and personal," Johnson said. "If Hillary Clinton gets in, it's going to be more of that."
At the rally, two women in costume acted out a coughing Clinton being led to prison by Trump. Inside the venue, a man wearing a "She's A C**t, Vote For Trump" T-shirt sat with his wife and children. While most audience members opt for a tamer message, "Trump That B***h" T-shirts have been a rally mainstay for months.
When Trump spoke that day, he paused at points to allow the crowd to scream in unison at the reporters covering the rally. Chants of "lock her up," the campaign's unofficial slogan, broke out before and during his remarks. "Lock her up is right," Trump, who has said he will prosecute and jail Clinton, responded.
Four days later in Greensboro, North Carolina, another crowd chanted "lock her up" — this time in reference to one of the women accusing Trump of unwanted sexual contact.
The women coming forward with stories of what they say was inappropriate behavior by Trump were the main topic of his speech that day. Trump, who counts among his fans people notorious for harassing perceived enemies on social media, urged the crowd to "check out" one accuser's Facebook page.
While Trump spoke, a burly man in a "Make America Great Again" cap put a protester in a headlock before security removed the activist, then walked around collecting high fives from rally-goers. As security came to remove him as well, the crowd began cheering, "Let him stay!"
Law and order
While past presidential nominees have taken care to distance themselves from unruly or threatening supporters, Trump has hinted, implied or outright stated that extremism in defense of Trump is no vice.
That message peaked during the primaries, when Trump, running on a platform of "law and order," routinely defended supporters who physically attacked protesters.
On the day of the Iowa caucuses in February, Trump told supporters he would pay for a lawyer if they "knock the crap out of" protesters he claimed were planning to throw tomatoes. Later that same month, as a protester was escorted out, Trump said he'd "like to punch him in the face, I tell ya."
In March, Trump said he would consider paying legal bills for a supporter who had sucker punched a protester on camera. He didn't "condone" the behavior, but the protesters, he said, were "very taunting."
These face-offs were a familiar ritual at Trump rallies until the candidate toned things down somewhat after protesters and supporters clashed at a March event in Chicago. His rallies now include a recorded request that audience members let security handle any disturbances. The largest subsequent outbreak of violence came from anti-Trump protesters, who threw eggs and attacked Trump supporters at an event in San Jose. But Trump also warned Republicans of "riots" if delegates denied him the nomination at the GOP convention.
"We see a lot of violence around Trump appearances where supporters think: 'Well, gee he's authorized me to do it,' even without a direct order," said Kim Lane Scheppele, a Princeton professor and expert on authoritarian regimes. "It creates a kind of culture of permission," Scheppele said.
Twice Trump has made jokes that seem to float the notion of Clinton being assassinated. In August he suggested "Second Amendment people" could prevent her from filling a Supreme Court seat. It was widely perceived as a reference to violence, although the campaign denied that was his intent. In September, he said Clinton's bodyguards should disarm and then "see what happens to her."
Trump has also shown unprecedented tolerance for supporters who engage in more overt threats.
He enthusiastically defended the character of an adviser, Al Baldasaro, after he repeatedly said Clinton "should be shot by a firing squad," even after his campaign distanced itself from the remarks.
Carl Paladino, the current chair of Trump's New York campaign, sent an email to a female anti-Trump Utah GOP delegate saying she should be "hung for treason" and promised to "be in your face" at the convention. Roger Stone, a longtime informal adviser to Trump, has regularly called for executing political opponents.
In the final weeks of the campaign, the candidate has cast himself as the victim of an unsubstantiated global conspiracy to rob him of the presidency — blaming almost everyone, including media outlets, election officials, banks, pollsters, Democrats, Republicans and his many female accusers.
Taking a cue from the nominee, one Trump voter told the Boston Globe that he plans to make minority voters "a little bit nervous" at election sites in response to the candidate's regular calls to watch for fraud at polling places. Others have raised the possibility of post-election unrest. The Trump campaign responded to the Globe article by saying they "reject violence in any form and will not allow it to be a part of our campaign."
For the most part, Trump supporters at recent events say they will accept the results of the election even as they question the process. Trump has complained that accusations his campaign remarks stoke violence are overblown and has accused activists of deliberately baiting his voters.
But the escalation in rhetoric, paired with Trump's longstanding reluctance to denounce extremist supporters, has civil rights groups worried that conditions are becoming dangerous.
This fear is especially pronounced because Trump has cast such a wide net in picking targets, and they often have a racial, ethnic, or religious component. He's regularly made false claims about American Muslims celebrating terrorism or refusing to turn in an attacker and warned that "other communities" — almost invariably cities with large minority populations — are out to steal the election. Recently, Trump told Fox News "illegal immigrants are voting all over the country."
"What happens on Nov. 9 is anyone's guess, but some of these trend lines of mainstreaming and broadening bigotry and incidents of violence and hints of a dark conspiracy are very concerning," Jonathan Greenblatt, CEO of the Anti-Defamation League, said in an interview.