Nine months after descending a very classy escalator and entering the presidential arena, Donald J. Trump has made one thing plain: You sell him short at your own risk.

Even as he kept rising in the polls, it took me a long time to realize he was no summer joke before voters and their parties got down to business. I finally got it after the San Bernardino terror attack in December, after President Obama addressed the nation from the Oval Office, mostly repeating his own earlier lines about how we “will overcome” “the threat from terrorism” and eventually “destroy ISIL,” calling its beliefs a “perverted interpretation of Islam” and asking Americans not to buy into the terrorists’ apocalyptic vision of a “war between America and Islam.”

The next day, Trump proposed his Muslim ban, “a total and complete shutdown of Muslims entering the United States until our country’s representatives can figure out what is going on.” It’s a loathsome and practically impossible idea and again, pundits predicted he’d finally gone too far. Again, voters disagreed. Six in 10 Republicans backed the ban, and he hit a new high in the national polls weeks ahead of the first contests.

A couple weeks after the attack, Obama conceded he’d underestimated American anxiety, reportedly telling newspaper columnists in an off-the-record session that he hadn’t watched enough cable news to get how much fear was out there. No one’s ever accused Trump of that particular sin of omission.

So Trump Trumped the President of the United States. All but sawed off the Ron and Rand branch of the Republican Party. Made it plain that 15 years after 9/11 we’re far from mastering our fear, that a husband and wife with some guns and bombs attacking an office party is enough to shake up the national conversation. Forget planes flying into buildings. Just try and imagine where our election goes if there’s a Paris-scale attack somewhere in the United States between now and November.

Trump himself seems to think that terror (as you’ll see, he’s not so good at specifying which attack he means, or going into the details about them, but he sure gets the concept) marked a turning point in his campaign. Looking back on his remarkable, terrifying ascent in his victory speech after winning four more contests Tuesday, Trump offered his own secret origin story for how his campaign went from something sort of serious to the real deal when “something happened. Something called Paris.”

Here’s Trump on Trump, worth quoting at length, and, for full effect, reading out loud:

“We came down the escalator, and it was about trade and it was about borders. And what happened is pretty quickly after that—and we were, we shot right up. I shot right to the top of the polls, and have been leading in the polls almost from the beginning, without fail. We went up in June. Most people said I’ll never run, he’s just going to have fun, he’s having a good time. This isn’t necessarily—I am having a good time. I’m having a very nice time. But you know what? I’m working very hard and there is great anger, believe me. There is great anger. One of the broadcasters was saying ‘Is there anger?’ and I said to him ‘I’m supposed to say: No, there’s not. We love the way things are working. We love the deal you made with Iran. It’s wonderful. You give them a hundred and fifty billion dollars. We get nothing. We love all the deals. The trade deals are wonderful. You lose 500 billion dollars a year with China. We lose 58 billion dollars a year in terms, in terms of imbalance. It’s a total imbalance. We don’t make good deals anymore. We don’t win anymore. As a country, we don’t win anymore. And they asked: Is there anger from your people? There seems to be—. And I said there is anger. They aren’t angry people. But they want to see the country properly run. They want to see borders. They want to see health care. They want to see things properly taken care of. They want our military rebuilt. Our military is in a very bad state—they want it rebuilt. Very very importantly—and they want the Second Amendment by the way protected, and protected strongly. And that’s going to happen. And you know what they want so badly? They want our veterans taken care of. Our veterans are treated so badly. So we started and something happened called Paris. Paris happened. And Paris was a disaster. That was, there have been many disasters, but—it was Paris. And then we had a case in Los Angeles where—it was in California where 14 young people were killed. And it just goes on and on and on. And what happened with me was, this whole run took on a whole new meaning. Not just borders. Not just good trade deals… But it took on a whole new meaning and the meaning was very simple: We need protection in our country. And that’s going to happen. And all of a sudden, the poll numbers shot up. And I’m just very proud to be a part of this.”

He’s right. Not in a moral sense. And not in a literal sense, given that a bunch of those numbers are wrong, that he doesn’t seem to know that San Bernardino isn’t Los Angeles, that it wasn’t young people who were killed there.

But he’s right, verifiably so, that he’s tapping into very real fears about free markets, open borders, and the costs of tolerance—fears that advocates of those good things brush off or sneer at. The rest of us underestimate or write off him or his supporters at our own risk.

A dirty little not-so secret: 54 percent of Republicans say they think Obama is a Muslim. And 60 percent support Truther Trump’s Muslim ban. It’s not hard to connect the dots here, and the picture isn’t pretty.

That said, if Trump’s the only person speaking to widely shared fears, the rest of us need to ask how it’s come to that, how the mainstream political discourse managed to alienate perhaps a third of all American voters.

Obama closed his post-San Bernardino address by imploring Americans: “Let’s make sure we never forget what makes us exceptional. Let’s not forget that freedom is more powerful than fear.”

Trump, the savviest exploiter of the media this side of ISIS, is taking the other side of that bet.