Jacquelyn Martin / AP

The critical last layer of Donald Trump’s support in 2016 came from voters uncertain that he belonged in the White House. Now he appears determined to test how much chaos they will absorb before concluding they made the wrong decision.

For all the talk about the solidity of Trump’s base, it’s easy to forget how many voters expressed ambivalence even as they selected him over Hillary Clinton. Fully one-fourth of voters who backed Trump said they did not believe he had the temperament to succeed as president, according to an Election Day exit poll conducted by Edison Research. That number rose to about three in 10 among both the independents and the college-educated whites who backed Trump, according to previously unpublished data provided to me by Edison.

Yet even as they expressed hesitation about the future president, those voters were still willing to take a risk on him, either because they disliked Clinton or wanted change or preferred to disrupt the political system. Some may have thought Trump would moderate his behavior in office.

It’s an understatement to say Trump has dashed those hopes. Instead, he has continued to shatter norms of presidential behavior in every possible direction. Allies and opponents alike usually attribute Trump’s volatility to personal factors: an impulsive and mercurial personality that lashes back at any perceived affront, seemingly without much thought about the long-term implications and with a reluctance to take advice or consider evidence.

But after two years, it’s also clear that Trump sees strategic value in violating presidential norms. He’s shown that he believes he benefits from immersing all of those around him in constant unpredictability. Probably even more important, he sees barreling through the informal guardrails that have constrained previous presidents as a way of signaling to his core supporters that he will go to any length to defend their interests. From that perspective, the more establishment voices condemn his behavior, the more he signals to his base that he’s fighting for them by any means necessary.

Until the midterm elections, it was common for Trump critics to lament that he paid little price for these excesses. But the November results showed, in a quantifiable way, that Trump’s belligerent and erratic behavior does carry a cost. Democrats won 40 seats in the House—and carried the national House popular vote by a larger margin than the GOP did in its 1994 or 2010 landslides—even though unemployment was below 4 percent and two-thirds of voters described the economy as either excellent or good. A performance that weak for the president’s party should not be possible with an economy that strong. But both independents and college-educated white voters, two groups that expressed widespread doubt about Trump’s temperament from the outset, broke solidly for Democrats last month after narrowly tilting toward him in 2016.

Rather than taking that shift as a sign to reconsider his course, Trump has doubled down on disorder since Election Day. He approaches the New Year engulfed in three distinct crises, all of which he ignited with his own actions.

Trump has precipitated a diplomatic crisis by abruptly announcing his intention to withdraw American forces from Syria. That triggered the resignation of Defense Secretary James Mattis, which reinforced the initial tremor over the sudden reversal with a powerful aftershock.

Trump has precipitated a governing crisis by forcing a partial federal shutdown through his demand for $5 billion in funding for his border wall—an ultimatum that the administration itself only a few days earlier acknowledged could not win 60 votes in the Senate.

And he’s instigated a financial-market crisis through the shutdown, his saber-rattling on trade with China, and his repeated Twitter attacks on Federal Reserve Chairman Jerome Powell—with Treasury Secretary Steven Mnuchin providing the aftershocks in this case through his amateurish efforts to calm the markets last weekend.

Trump defenders argue that, on the merits, he can win each of these fights politically (though that case seems very tenuous for the border wall, which has faced majority opposition in virtually every public poll conducted during his presidency). But the larger risk to Trump is that the virtues of each of his positions become indistinguishable amid such swelling levels of confrontation and instability; arguing for any individual policy in this environment may be like trying to identify a single wave in a flood tide.

Each of the current crises may recede in 2019, but the overall trajectory of Trump’s presidency points toward more, not less, disorder. Trump has systematically dismissed advisers such as Mattis who were considered, however imperfectly, the most powerful constraints on his behavior. And Trump will face new provocations that are likely to trigger his most belligerent impulses—especially from an incoming Democratic House majority that’s poised to investigate every aspect of his presidency (including his personal finances). Looming close behind are more potential indictments from Special Counsel Robert Mueller and the release of his final report on Trump, Russia, and the 2016 campaign. In 2019, combustion may be as great a risk to Trump as collusion.

As the stock market has nosedived in December, it’s become common for financial traders to tell business reporters that they now see concrete danger in Trump’s Twitter and press-conference tirades, which they once treated as only “background noise” behind policies that they generally supported.

But since their November losses, strikingly few congressional Republicans have echoed that verdict. Even amid the current maelstrom, very few have publicly broken with Trump over the shutdown or his attacks on the Fed. And while some have criticized his Syria decision and lamented Mattis’s departure, hardly any have acknowledged the broader concerns about Trump’s decision making and stability that both developments provoke.

The market meltdown in particular may be creating the most pressure Trump has yet felt to temper his behavior. But so long as congressional Republicans refuse to publicly demand change, the waves of chaos emanating from the Oval Office are likely to only grow higher. Through their deferential silence, Republicans are betting they can withstand those waves better in 2020 than they did in 2018.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.