A conventional politician, having won the presidency with a negative popular-vote margin, would likely spend his time in office trying to broaden his base and, by extension, his path to re-election.

Not so Donald Trump, who seems intent on winning the White House in 2020 by running with the same rhetorical playbook that carried him to an unlikely victory two years ago. Starting with the vision of “American carnage” he conjured in his inaugural address, Trump has governed with the same divisive dystopianism that marked his campaign, loudly narrowcasting to his most ardent supporters with little apparent regard for who else hears him.

That monomaniacal focus on his base has been on especially stark display in the wake of voters’ crippling rejection of the Trumpian GOP — a ballot box message Trump has ignored, partially shuttering the government just before Christmas over his unpopular wall-with-Mexico idea.

This approach is both a source of strength for the president and, quite possibly, a politically fatal weakness.

It is a strength because it has helped bind his supporters to him: He retains strong support among a group that makes up somewhere between 35 to 40 percent of the electorate, as the most recent NBC/Wall Street Journal poll illustrates. At the heart of that Trump base are white men without college educations who have felt both buffeted by social and economic changes and angry at a system that they feel ignores and is rigged against them.

“The hot core of Trumpism is a group of Americans who are the perfect marks for a con-man like Trump: Anxious over economic and social status markers in a changing world,” Never-Trump GOP strategist Rick Wilson wrote in his book, “Everything Trump Touches Dies.” “Sure, they’re looking for a place for both their anger and uncertainty to be heard. But they’re also looking for someone to blame.”

Trump gives them that. If Richard Nixon kept his enemies list in secret, Trump posts his on social media: the press, immigrants from Central America, Muslims, the growing constellation of former employees testifying against him, football players who kneel during the national anthem, political appointees he once deemed great but are suddenly dangerously incompetent (Federal Reserve Chairman Jerome Powell and outgoing Secretary of Defense James Mattis come to mind) and foreign countries not named Russia, to name a few. And he does it while showering his supporters with the attention they felt deprived of by setting up an us-versus-them, grievance-based dichotomy that is catnip to his voters.

Traditional presidents, impressed with the gravity of being leader of the whole country (as well as being motivated by the aforementioned desire to get more adherents) have couched even their appeals to their core supporters in ways that don’t alienate others. But Trump doesn’t bother with dog-whistles; he just barks.

“There is a way of speaking to your base that is more inclusive,” says Jeff Shesol, who was a speechwriter for President Bill Clinton. But, he adds, Trump is “desperate for affirmation and to try to broaden ... to the middle of the American electorate would have really required work, would have really required him to find something in himself which he really doesn’t have.”

It’s a symbiotic relationship: Trump revels in his supporters’ adulation, while they bask in the fact that when he speaks it’s to them and them alone. If few politicians talk like Trump, it’s because few have plucked the strings of authoritarianism as nakedly as he has. And his supporters conflate crass demagoguery with authenticity. “They like the fact that he isn’t couching things in high-level, safe terms,” says a Democratic pollster with extensive experience in red states. “They think he talks straight and he’s honest in the way he talks to people.”

Of course, Donald Trump is manifestly not honest. He is a fabricator without parallel in U.S. history; and the pace of his prevarications has only increased. Not that this particularly undercuts his core support, for a combination of reasons.

Most obviously, some Americans underestimate the breadth and depth of his mendacity, in no small part because they mistrust the media more than their leader. His status as a businessman also affords him greater leeway because people know he’s a salesman and that salesmen embellish; in their view he is speaking larger truths about them and the country, so the details are less important.

“It’s also what he’s doing,” says the Democratic pollster. “He’s a wrecking ball. They’ve been ignored and he’s paying attention to them. And the thing that ignored them … he’s just smashing.”

Whit Ayres, a veteran Republican pollster and Trump critic, recalled a focus group he ran in the spring that helped him understand support for the president. “We get the joke about Trump,” Ayres recalled them saying. “We understand that he’s a bear to work for and in many ways he’s not a nice person.”

“But we live in communities where most of our manufacturing jobs have been shipped overseas, opioids are ravaging our communities, our families are coming apart,” they added, according to Ayres. “And we were faced with a choice between a man who said he’d help us and a woman who called us deplorable. What the hell did you expect us to do?”

But while Damn the other voters, full speed ahead! worked against Hillary Clinton (with both her quarter-century of Republican-primed baggage and the campaign’s take-the-Midwest-for-granted strategy, not to mention James Comey’s and Vladimir Putin’s fingers on the scale) it hasn’t produced much beyond thrashing and smashing in office. Is it likely to carry Trump to victory again in two years?

“It’s either rewriting the rules of politics or it is spectacularly self-destructive politically,” says Shesol. But early signs point to the president getting burned by the Trumpster fire he has so gleefully stoked.

His base may be a rock-solid 35 percent, but he has trouble pushing his approval rating into the mid-40s — and you could see the fruit of Trump’s approach in the midterm elections, when Democrats gained 40 seats. “It’s a problem when you’re in a government of the people, by the people and for the people and a majority of the people are against what you’re trying to do,” says Ayres.

Republican pollster David Winston sifted through polling data from the election and determined that Trump’s manic focus on immigration leading up to Election Day was “popular with the base and those at President Trump’s rallies but also controversial and divisive, particularly with Independents,” he wrote in a report. “The people who made their decision over the last few days voted Democratic by a 12-point margin.”

Winston noted that the demographic makeup of the electorate didn’t change drastically from 2016 to 2018; but the GOP got wiped out because especially suburban voters deserted the party. As alarming for Republicans, CNN’s Ron Brownstein noted, “Democrats ran much more competitively among the roughly half of [white working-class voters] who are not evangelical Christians,” and especially among white, nonevangelical women. Given that Trump’s Electoral College victory was built on an 80,000-vote margin in three states, he can’t afford even small fracture in his base.

Republicans in suburban districts say that Trump was a toxic drag. They have a point: Running up his margins in states he’s going to win anyway won’t help Trump if suburbanites abandon him in swing states as they did last month.

And yet here we sit: One quarter of the government — including, (irony is not dead!) the Department of Homeland Security — is darkened while Trump wallows in a fog of invective and grievance. Why? Because the president, spurred by the interlocutors with his base who make their money in the conservative-entertainment complex, has decided to treble down on his wall. “Trump’s advisers acknowledged that the funding may not be secured in the end but boasted that the spectacle would be remembered favorably by his base voters as proof of his mettle,” The Washington Post reported last week.

Like the shutdown, Trump’s beloved barricade enjoys greater support among his base than among the broader electorate. The shutdown and the wall, then, are Trump’s latest performance art pieces. They’re aimed at his base, a show of strength, power and devotion with the rest of us an unwilling and increasingly unhappy audience.