As with most things Trump, the furor over the “fire and fury” has divided the nation in two — those who believe the president is a loose cannon, impulsively blurting whatever flits through his mind, and those who believe his inflammatory talk is a wily combination of politically savvy instincts and a gut-driven populism that simply aims to please.

When President Trump went off script Tuesday to deliver a startling threat to North Korea — “They will be met with fire and fury like the world has never seen” — it was as if the nation relived the most lurid themes of the 2016 campaign in one chilling moment.

Last fall, Hillary Clinton’s ­campaign used as one of its final weapons a TV ad featuring a longtime nuclear missile launch officer who warned against voting for Trump: “I prayed that call would never come. Self-control may be all that keeps these missiles from firing.”

Then, quick-fire, a series of clips of Trump on the stump: “I would bomb the s--- out of them.” “I want to be unpredictable.” “I love war.”

“The thought of Donald Trump with nuclear weapons scares me to death,” Bruce Blair, the retired launch officer, says in the ad. “It should scare everyone.”

(Elyse Samuels/The Washington Post)

It very nearly did: Voters made clear last fall that they trusted Clinton vastly more than Trump on the use of nuclear weapons — by 57 percent to 31 percent in a Fox News poll in October, for example.

But Trump voters often said that their reasons for supporting him outweighed their sense that he could be dangerously impulsive — and they repeatedly expressed confidence that the national security apparatus would keep him in check.

Now, facing a reality test of that theory, Americans are coming to conclusions both predictable and surprising.

Trump’s critics tend to view his “fire and fury” threat as evidence of a president gone over the edge.

“Trump is fulfilling expectations of someone who lashes out dangerously at real and perceived challengers,” said Blair, who is now a research scholar at Princeton University. “He is raising the risk of a conflict that escalates to nuclear war. He has proven time and again to be . . . unable to apply a deft hand at diplomacy.”

But the president’s defenders see him working from the gut, with admirable instincts to protect the nation and take pride in American power.

(Victoria Walker,Danielle Kunitz/The Washington Post)

Fred Doucette, a longtime Trump supporter who is assistant majority leader in New Hampshire’s House of Representatives, watched Trump’s appearance Tuesday. He was disappointed Trump didn’t declare a national emergency on opioid abuse but was pleased to hear the president deliver a strong message to North Korea.

“The president spoke in a language that Kim Jong Un understands — and, personally, I think they should follow up on that and show them that we mean business,” said Doucette, 52, a Navy veteran and retired firefighter and paramedic. “I assume the president spoke with his generals and his Cabinet first.”

Secretary of State Rex Tillerson said the president’s remarks were no harbinger of imminent nuclear war but rather tough talk designed to send Kim a clear message. “Americans should sleep well at night,” Tillerson said.

Doucette said he does exactly that. “When the phone rings at 3 a.m., I want Donald Trump to be the president that answers that phone call,” he said. “I sleep well at night with President Trump, very well.”

Last fall, 10 former Air Force nuclear launch officers issued an open letter warning that Trump “should not be entrusted with the nuclear launch codes . . . He has shown himself time and again to be easily baited and quick to lash out, dismissive of expert consultation and ill-informed of even basic military and international affairs.”

But on Wednesday, those officers were no longer united in their view of Trump.

“The reaction to this is not wholly rational,” said one of the signatories, who spoke on the condition of anonymity because his employer had not authorized him to speak publicly. “A lot of people are caught up on Trump the character — and he is erratic — without thinking about whether there’s historical precedent for this kind of language. I’m actually a little relieved that Trump is crawling inside the North Koreans’ helmets. I would not have chosen those words, but he did put the fear of God into them.”

But another of the former “missileers” said Trump’s fiery rhetoric was evidence of exactly what he had warned about last fall. “He speaks impulsively, and he acts impulsively, and I don’t know what restraints there are on President Trump,” said Mark Lussky, a retired lawyer who served on a missile combat crew from 1972 to 1976. “He doesn’t know how to back down on anything.”

At the core of the anxiety over Trump’s remarks is the worry that the president made his threat without consideration of what might follow. The sheet of paper he held in his hand was about opioid abuse, not the conflict with North Korea. Yet the White House was quick to issue assurances that, as press secretary Sarah Huckabee Sanders said, although Trump’s “words were his own . . . the tone and strength of the message were discussed beforehand” by Chief of Staff John F. Kelly and members of the National Security Council.

Presidents don’t usually improvise comments on global crises. “What would be ‘normal’ in the Bush or Obama or Clinton administrations would be for the combination of strategic communications people and policy people — including the national security adviser — to develop, in consultation with the State Department and the Defense Department, a messaging strategy with top lines that they felt the president needed to emphasize,” said a senior diplomat who served in all three administrations.

To many Trump critics, the president’s remarks were of a piece with what seems like a casual attitude toward wielding the unfathomable power of the United States’ arsenal. On the campaign trail, he said that any Iranian vessels that “make gestures at our people . . . will be shot out of the water.” Trump, who attended a military academy as a teenager and repeatedly avoided the draft for the Vietnam War, had hoped to add tanks and heavy military equipment to his inaugural parade in January but was overruled.

Trump was dining with Chinese President Xi Jinping at Mar-a-Lago in early April when he authorized an airstrike on a Syrian airstrip. As he later described the moment, “We’re now having dessert. And we had the most beautiful piece of chocolate cake that you’ve ever seen, and President Xi was enjoying it. And I was given the message from the generals that the ships are locked and loaded, what do you do? And we made a determination to do it, so the missiles were on the way.”

The Clinton campaign ran ads focused on Trump as commander in chief throughout October, including one spot that showed Trump asking, “Why can’t we use nuclear weapons?”

“One of the great concerns voters had, particularly independent voters, was the threat of somebody that impulsive, that erratic, that unprepared, having control over the nuclear codes,” said Jim Margolis, the campaign’s media adviser.

Some of those voters acknowledged Trump’s erraticism yet voted for him anyway.

“There may have been a presumption that if elected, Trump would settle down, become more presidential, less crazy in his taunts, and that the cocoon of security advisers around him would keep him in check,” Margolis said. “Clearly, that presumption was wrong.”

Another anti-Trump spot, made by a super PAC run by former senator Bill Bradley (D-N.J.), targeted Ohio voters and evoked the famous 1964 “Daisy” ad for President Lyndon B. Johnson that capi­tal­ized on fears that his Republican challenger, Barry Goldwater, was too reckless to be trusted with nuclear codes.

Bradley’s ad showed the mushroom cloud of an atomic bomb detonating, and it showed TV host Chris Matthews telling Trump that “nobody wants to hear” a presidential candidate talk about using nuclear weapons.

“Then why are we making them?” Trump replies.

Karen DeYoung contributed to this report.