Every once in a while, a politician says something so outrageous that it produces not the feigned outrage that has become so familiar but genuine outrage. That’s what President Donald Trump managed this week when in a press conference he was asked about his public silence on the four American soldiers who were killed in Niger. He claimed that while he calls the families of those killed in action to express his condolences, previous presidents, particularly Barack Obama, hadn’t done so.

This was a particularly despicable lie because it painted Obama — and other presidents, but let’s be honest, mostly Obama — as cruel and dismissive when it comes to the sacrifice of those in uniform, while portraying Donald Trump as the only one who truly cares.

The next morning, Trump actually seemed to double down. In an interview with Fox News’ Brian Kilmeade, he referred to the fact that the son of his chief of staff, John Kelly, was killed in Afghanistan in 2010:

“I mean, you could ask General Kelly did he get a call from Obama. You could ask other people. I don’t know what Obama’s policy was. I write letters and I also call. . . . This was, again, fake news CNN. I mean, they’re just a bunch of fakers.”

It would be easy to just add this to the mountain of lies Trump has told, but it’s worth taking a moment to examine it, because it provides an important window not only into his own thinking but the way that this president is succeeding in making the entire country stupider and more misinformed on an ongoing basis.

Let’s begin with Trump’s words at the press conference. He was asked, “Why haven’t we heard anything from you so far about the soldiers that were killed in Niger [on Oct. 4]?” and he replied that he had written letters to the families, though those letters hadn’t yet been sent, and that he’d be calling them at some point. Then came this:

“So, the traditional way — if you look at President Obama and other presidents, most of them didn’t make calls, a lot of them didn’t make calls. I like to call when it’s appropriate, when I think I’m able to do it.”

A few minutes later, another reporter circled back to this question, asking how Trump could claim that President Obama didn’t call the families of fallen soldiers. Here’s part of his response:

“I don’t know if he did. No, no, no, I was told that he didn’t often. And a lot of presidents don’t; they write letters. I do. . .

“President Obama I think probably did sometimes, and maybe sometimes he didn’t. I don’t know. That’s what I was told. All I can do — all I can do is ask my generals. Other presidents did not call. They’d write letters. And some presidents didn’t do anything. But I like the combination of — I like, when I can, the combination of a call and also a letter.”

It’s obvious from his responses that Trump had absolutely no idea what presidents before him did or didn’t do in this situation, which he admitted again (“I don’t know what Obama’s policy was”). Yet he went ahead and claimed that only he calls the families.

This is quite familiar to anyone who’s been watching Trump these last couple of years. He takes his own limited experience and characterizes it as unique, extraordinary and unprecedented. No one has ever done this before, no one has accomplished so much, no one knows more than I do. There’s an element of the salesman’s puffery at work, but it also comes from a place of pure ignorance.

As conservative writer Tim Carney hypothesized last week, when Trump claims that no administration has ever done as much as his, it isn’t so much that he’s intentionally lying but that he’s so ignorant of the presidency and politics in general. He never realized that presidents and their staffs work very hard (“Like how 10-year-old me assumed teachers went into a cocoon at 3 p.m.,” Carney said), so he assumes he must be the first to have ever done so. The comparison to a 10-year-old is apt, because Trump’s brand of ignorance is so infantile. All of us are ignorant about some things, but only Trump believes that if he doesn’t know something, no one else could possibly know it either (“Nobody knew that health care could be so complicated”).

When a normal person is in a state of ignorance, he or she might exercise some caution and refrain from making a volatile accusation that, for instance, his or her predecessors were callous to Gold Star families. But not Trump. You’ll notice that the first time he says it, he asserts it as simple fact: “if you look at President Obama and other presidents, most of them didn’t make calls.” When he’s challenged, he equivocates: “I don’t know if he did . . . President Obama I think probably did sometimes, and maybe sometimes he didn’t. I don’t know. That’s what I was told.”

Now here’s why this matters. Yes, many news outlets pointed out that Trump wasn’t telling the truth. But there are probably three interns at Fox News who are now scouring old news reports to find some family member of a fallen soldier who didn’t get a call from Obama. If they find it, that person’s story will then become the subject of a segment on Sean Hannity’s show, and it will then get retold on a hundred talk radio programs and conservative websites as proof that Obama was a monster and the media are all lying about this. (Trump’s insistence that there was “fake news” at work is another way of telling his supporters not to believe whatever they hear about this subject that comes from sources not explicitly supporting him.) And I promise you that if you took a poll two weeks from now, you’d find that 40 percent of the public (or more) believes that Barack Obama never called the family of any fallen soldier, and only Donald Trump has the sensitivity to do so.

And that’s how Trump takes his own particular combination of ignorance, bluster and malice and sets it off like a nuclear bomb of misinformation. The fallout spreads throughout the country, and no volume of corrections and fact checks can stop it. It wasn’t even part of a thought-out strategy, just a loathsome impulse that found its way out of the president’s mouth to spread far and wide.

If you’re one of those who marvel at the fact that Trump’s approval ratings aren’t even lower than they are, this is a big reason why. It’s absolutely necessary to correct Trump’s falsehoods, but we shouldn’t fool ourselves into believing that any poisonous lie he tells won’t find an eager audience. And the whole country gets dumber and dumber.

Paul Waldman is a senior writer at The American Prospect.