(Gillian Brockell/The Washington Post)

Seeking and winning the presidency has been a magical voyage of discovery for Donald Trump.

Tuesday night, he divulged a most remarkable finding: Abraham Lincoln was — are you sitting down for this? — a Republican.

“Most people don’t even know he was a Republican,” Trump told a group of Republicans. “Right? Does anyone know? A lot of people don’t know that.”

It’s possible that somebody doesn’t know that Lincoln, the first Republican president, was a member of the Republican Party, also known as “the Party of Lincoln.” But it has not been for lack of effort on Trump’s part. He has repeatedly tried to educate the populace on this little-known fact.

August 2016: “Most people don’t know this. The Republican Party is . . . the party of Abraham Lincoln.”

September 2016: “A lot of people don’t realize that Abraham Lincoln, the great Abraham Lincoln, was a Republican.”

October 2016: “A lot of people don’t know that it’s the party of Abraham Lincoln.”

Beyond this Lincoln revelation, Trump has happened upon many other things that people didn’t know. Such as the complexity of health care: “Nobody knew health care could be so complicated,” he said recently. And the existence of abolitionist Frederick Douglass, who died in 1895: “Frederick Douglass is an example of somebody who’s done an amazing job and is being recognized more and more, I notice.”

Later, touring the new African American history museum in Washington, Trump discovered that slavery was bad. Spying a stone auction block, Trump said, according to Alveda King, a part of his entourage: “Boy, that is just not good. That is not good.” King also told the Atlanta Journal Constitution that upon seeing shackles for children, Trump remarked: “That is really bad. That is really bad.”

Who knew?

Trump’s discoveries of seemingly obvious things raise two possibilities: 1) He thinks people are awfully stupid, or 2) he is discovering for himself things the rest of us already knew. Which is true? Nobody knows. But we do know that there are many other things Trump thinks people don’t know about.

Sunday school: “I talk about Sunday school and people don’t even know what I’m talking about anymore. It’s true.”

That Bill Clinton signed NAFTA: “A lot of people don’t know that.”

What a value-added tax is: “A lot of people don’t know what that means.”

That we have a trade deficit with Mexico: “People don’t know that.”

That Iraq has large oil reserves: “People don’t know this about Iraq.”

That war is expensive: “People don’t realize it is a very, very expensive process.”

That the country is divided: “People don’t realize we are an unbelievably divided country.”

Thank you, Captain Obvious.

Trump, in his bid to educate the public about things he has learned, takes on a professorial tone. Talking about the Johnson Amendment on church-state separation, Professor Trump told an audience that it’s something “people don’t know in the kind of detail and depth that I have explained it to you today.” Trump had just explained to them the Johnson Amendment’s provenance: “This was Lyndon Johnson in the 1970s.”

The Johnson Amendment was passed in 1954. Johnson retired in 1969 and died in 1973.

Trump claims that “a lot of people don’t know” that U.S. taxes are the world’s highest and that “nobody knows” the U.S. murder rate is the highest in 45 years. For good reason: Those things aren’t true. Conversely, just about everybody knows that Russia was behind the election hacking, but Trump long asserted that “nobody knows if it’s Russia.”

While Trump has said “nobody knows everything,” he claims to come pretty close. In his own words:

“Nobody knows health care better than Donald Trump.”

“Nobody knows the tax code better than I do.”

“Nobody knows politics better than I do.”

“Nobody knows the politicians better than me.”

“Nobody knows the system better than me.”

“Nobody knows more about debt. I’m like the king.”

By contrast, Trump’s list of things other people don’t know about is extensive: the heroin problem in New Hampshire, Ben Carson’s performance in the primaries, President Obama’s record on deportations, the number injured in the Paris terrorist attacks, the hikes in Obamacare premiums, eminent domain, the existence of two Air Force One planes, Afghanistan’s mineral deposits, Hillary Clinton flunking a bar exam and the authenticity of Trump’s hair.

Trump may be correct when he says most people don’t know how much he’s worth and don’t know that he’s a “nice person.” But he’s surely wrong when he says people don’t know how bad things are.

“A lot of people don’t know it, but our country’s in trouble,” he has said.

If we didn’t know it before, we do now.

Twitter: @Milbank

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