Tonight, Donald J. Trump accepted the Republican Party’s nomination for president of the United States.

And I am, for the first time since I began covering American politics, genuinely afraid.

Donald Trump is not a man who should be president. This is not an ideological judgment. This is not something I would say about Mitt Romney or Marco Rubio. This is not a disagreement over Donald Trump’s tax plan or his climate policies. This is about Trump’s character, his temperament, his impulsiveness, his basic decency.

Back in February, I wrote that Trump is the most dangerous major candidate for president in memory. He pairs terrible ideas with an alarming temperament; he's a racist, a sexist, and a demagogue, but he's also a narcissist, a bully, and a dilettante. He lies so constantly and so fluently that it's hard to know if he even realizes he's lying. He delights in schoolyard taunts and luxuriates in backlash.

He has had plenty of time to prove me, and everyone else, wrong. But he hasn’t. He has not become more responsible or more sober, more decent or more generous, more considered or more informed, more careful or more kind. He has continued to retweet white supremacists, make racist comments, pick unnecessary fights, contradict himself on the stump, and show an almost gleeful disinterest in building a real campaign or learning about policy.

He has, instead, run a campaign based on stoking fear and playing to resentment. His speech tonight invoked a nightmarish American hellscape that doesn't actually exist. His promise to restore order made him sound like the aspiring strongman his critics fear him to be. "I have a message for all of you: the crime and violence that today afflicts our nation will soon come to an end," he said. "Beginning on January 20th 2017, safety will be restored."

Here is what we know — truly know — about Trump. Here is why he should not be president.

Trump is vindictive. So far, the unifying theme of Trump’s convention is that the leader of the opposition party should be thrown in jail. Trump didn’t like the Washington Post’s coverage of his campaign, so he barred its reporters from his rallies and threatened to use the power of the presidency to bring an antitrust suit against the Post's owner, Jeff Bezos.

He was upset that Ohio didn’t vote for him, so he sat its delegation in the cheap seats, even though the state is hosting the convention. He was angry about an interview his ex-ghostwriter gave to the New Yorker, so he sent his lawyers after him. He hates the protesters who interrupt his campaigns, so he said he would look into paying the legal fees of a supporter who sucker-punched one of them.

Imagine Donald Trump with the powers of the presidency. Imagine what he could do — what he would do — to those who crossed him.

Trump is a bigot. Donald Trump kicked off his campaign calling Mexican immigrants murderers and rapists. He responded to Ted Cruz’s surge in Iowa by calling for a ban on Muslim travel. He sought to discredit a US-born judge by saying his rulings were suspect because of his "Mexican heritage." Trump’s campaign is certainly the first time in my memory that a sitting speaker of the House has had to describe something his party’s nominee said as "the textbook definition of a racist comment."

This is not a man who should be put in charge of an increasingly diverse country that needs to find allies in an increasingly diverse world.

Trump is a sexist. Stories of Trump’s casual sexism abound, but during the campaign, it was women who questioned him who felt the full force of his misogyny. The first Republican debate, for instance, was hosted by Fox News and moderated by Megyn Kelly, Bret Baier, and Chris Wallace. Kelly wasn’t obviously tougher on Trump than her colleagues, but she was the antagonist he focused on, retweeting a follower who said she was "a bimbo" and saying she had "blood coming out of her … wherever."

After Carly Fiorina challenged him in a debate, Trump said to Rolling Stone, "Look at that face. Would anyone vote for that? Can you imagine that, the face of our next president?" After Hillary Clinton needed to take a bathroom break during a debate, Trump told the crowd, "It's too disgusting. Don't say it, it's disgusting."

It’s not just during political campaigns that this side of Trump emerges. Trump once told his friend Philip Johnson that the secret to women was "[y]ou have to treat 'em like shit."

Trump is a liar. Trump boasts constantly that he had the judgment and foresight to oppose the Iraq War. But he didn’t. On September 11, 2002, Trump was asked by Howard Stern whether he supported the invasion of Iraq. "Yeah, I guess so," he replied. Trump has not sought to explain these comments or offer evidence of an alternative judgment he offered elsewhere. He just lies about this, and he does so often.

But that’s true for Trump across many issues. He says his health care plan will insure everyone, when it will do nothing of the kind. He says his tax plan raises taxes on the wealthy when it actually cuts them sharply. Trump has lied about his net worth, his reasons for not releasing his tax returns, and his charitable donations. He lies easily, fluently, shamelessly, constantly.

Trump is a narcissist. Trump’s towering self-regard worked for him as a real estate developer. His real business was licensing his name out for building, menswear, golf courses, steaks. A bit of a narcissism is necessary to become a global brand. But the trait is maladaptive in a presidential candidate.

The most recent example was the 28 minutes he spent talking about himself when he was supposed to be introducing Mike Pence, his vice presidential candidate, for the first time. The most grotesque example was when he responded to the deadliest mass shooting in American history by tweeting, "Appreciate the congrats for being right on radical Islamic terrorism."

Trump admires authoritarian dictators for their authoritarianism. When MSNBC's Joe Scarborough asked Trump about his affection for Vladimir Putin, who "kills journalists, political opponents and invades countries," Trump replied, "He's running his country, and at least he's a leader, unlike what we have in this country."

But it’s not just Putin. Trump has praised Saddam Hussein because "he killed terrorists. He did that so good. They didn't read them the rights." He said "you've got to give [Kim Jong Un] credit. He goes in, he takes over, and he's the boss. It's incredible." It’s not just that Trump admires these authoritarians; it’s that the thing he admires about them is their authoritarianism — their ability to dispense with niceties like a free press, due process, and political opposition.

Trump is a conspiracy theorist. Trump burst onto the scene as a leader of the absurd "birther" movement. He’s said that Bill Ayers is the real author of Barack Obama’s Dreams From My Father, explained that the unemployment rate in America is really over 40 percent, and suggested that both Antonin Scalia and Vince Foster were murdered.

Trump is very, very gullible. This is related to his conspiracy theories, but Trump has a habit of believing and retweeting bad information that sounds good to him at the time.

This has led to, among other things, Trump retweeting false crime statistics, Trump retweeting Mussolini quotes from a Twitter account called Il Duce, Trump promoting a fake video claiming a protester who rushed his stage was sent by ISIS, and Trump endorsing a National Enquirer report suggesting Ted Cruz’s dad helped kill JFK. When pressed about these sundry embarrassments, Trump said, "All I know is what’s on the internet."

That’s a reasonable response from your uncle who forwards you weird email chains, but not from a presidential candidate.

Trump doesn’t apologize, and his defensiveness escalates situations. On Monday night, it became very clear that Melania Trump’s 2016 convention speech had lifted two paragraphs from Michelle Obama’s 2008 convention speech. The error was an embarrassment, but it could have been dispatched quickly by simply admitting fault and apologizing.

Instead, the Trump campaign turned it into a multi-day story and a character issue by denying anything had happened and blaming Hillary Clinton. This is "an example of when a woman threatens Hillary Clinton, how she seeks out to demean her and take her down," said campaign chair Paul Manafort, in one of the most genuinely ridiculous comments in recent American history.

The campaign also tried to argue that Michelle Obama doesn’t own the English language, and that similar language was used by Twilight Sparkle, a My Little Pony (I’m serious). Finally, days later, the Trump campaign admitted there was plagiarism and blamed a miscommunication between Melania and her speechwriter.

1. Deny everything.

2. Blame Hillary Clinton.

3. Blame My Little Pony.

4. Deny everything.

5. Confess & apologize. — Binyamin Appelbaum (@BCAppelbaum) July 20, 2016

A similar pattern played out when Trump tweeted an anti-Hillary meme that superimposed a Star of David atop a pile of money and accused Clinton of corruption. The image was obviously anti-Semitic, and the Trump campaign quickly took it down. But Trump himself went on a Twitter rampage, arguing that what was clearly a Star of David was actually just a sheriff’s star, or maybe just a regular old star, and that the campaign shouldn’t have removed the offending meme in the first place.

So far, these examples are farce, but as Tim Lee writes, this tendency in the Oval Office could lead to tragedy: "[Trump’s] behavior on the campaign trail suggests that he would be unlikely to admit mistakes and defuse tense situations. Instead, his first instinct would be to escalate every conflict in an effort to bully foreign adversaries into giving him his way. That might work in some cases. But in others — especially against powerful countries like China or Russia — the results could be disastrous."

Trump surrounds himself with sycophants. It's tradition for presidential candidates to release a note from their physician testifying to their fitness to fulfill the duties of the presidency. On December 14, Donald Trump submitted his entry to this quadrennial custom.

"If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency," Dr. Harold Bornstein writes. "His blood pressure, 110/65, and laboratory test results were astonishingly excellent. … His physical strength and stamina are extraordinary."

This is … not how most doctor notes read. "Reached for comment regarding this, a spokesperson at the American Medical Association just giggled," reported the Daily Beast.

There are many positions where one might accept a pliable crony. But "personal physician" should not be one of them. The fact that Trump would entrust his health to a doctor who would sign off on a note like this should terrify his family and friends. But more than that, it should disqualify him from the presidency.

Trump has proven too lazy to learn about policy. Trump didn’t know much about policy when the campaign started, and as far as anyone can tell, he hasn’t made any obvious effort to rectify that.

The latest and most damaging example is his interview with the New York Times, in which he said he would not automatically defend NATO countries against attack from Russia. It’s not obvious Trump meant to say that, or even knew what saying that meant, as Manafort immediately began denying Trump had ever said it. (The Times subsequently released a transcript showing that, yes, Trump had said it.)

But this is a pattern for Trump, who doesn’t bother to come up with convincing answers even to obvious questions, and definitely has not put in the time to develop a deep understanding of the issues he might face as president. As Matt Yglesias wrote, this is very much a choice Trump has made. "Trump is now the GOP nominee, and there are hundreds of professional Republican Party politicians and operatives around the country who would gladly help him become a sharper, better-informed candidate. It doesn’t happen because he can’t be bothered."

Trump has run an incompetent campaign and convention. As brilliant as Trump has been in securing media attention for himself and channeling the anxieties of conservative voters, he hasn’t bothered to build a real campaign organization, and his convention has been a festival of unforced errors.

This is the context of Melania Trump’s plagiarism, of Ted Cruz’s anti-endorsement, of the night that was supposed to be about jobs and the economy but was actually about Benghazi and jailing Hillary Clinton. In isolation, these are gaffes, mistakes, bad luck. Together, though, they tell a damning story of organizational incompetence.

The most generous interpretation of this is that Trump is capable of running an effective organization, but he’s just not interested in conventions and field operations in the way he is interested in golf courses and condos. Others have certainly testified to the trouble Trump has focusing on tasks that don’t engage him. His former ghostwriter says, "He has no attention span." Unfortunately, the president actually needs to focus on all kinds of dull and unpleasant tasks.

Trump is a bully. Trump won the Republican nomination by proving that even adults can be bullied with schoolyard taunts. There was "low-energy Jeb," and "Little Marco," and "Lyin’ Ted," and now we’ve got "Crooked Hillary." Trump made fun of Rand Paul’s looks and Chris Christie’s weight and Carly Fiorina’s face and a New York Times reporter’s physical disability.

It seems like this shouldn’t have to be said, but it’s better to be kind than cruel, and there’s a deep, instinctual cruelty in Trump — he finds people’s weak spots, their insecurities, and he exposes them in front of crowds.

Trump has regularly incited or justified violence among his supporters. At a rally in St. Louis, Donald Trump lamented that "nobody wants to hurt each other anymore."

Yes, lamented.

The topic was protesters, and Trump's frustration was clear. "They're being politically correct the way they take them out," he sighed. "Protesters, they realize there are no consequences to protesting anymore. There used to be consequences. There are none anymore."

Earlier in the campaign, two of Trump’s supporters attacked a homeless Mexican man and told the police, "Donald Trump was right — all these illegals need to be deported." Trump’s response? "I will say that people who are following me are very passionate. They love this country and they want this country to be great again."

The simple fact of it is that Donald Trump should not be president of the United States. That is not because he is too conservative, as some Democrats would have it, or because he is not conservative enough, as many Republicans would have it. It’s because the presidency is a powerful job where mistakes can kill millions, and whoever holds it needs to take that power seriously and wield it responsibly. Trump has had ample opportunity to demonstrate his sense of seriousness and responsibility. He has failed.

It is said that the benefit of America’s long presidential campaigns is they offer the candidates time to show us who they really are. Trump has shown us who he really is. He is a person who should not be president. That he is being brought this close to the presidency — that he is one major mistake by Hillary Clinton away from winning it — should scare us all. It certainly scares me.

Watch: How the Republican Party went from Lincoln to Trump