Donald Trump supporter Kristen Peterson of Huntersville, N.C., chants "show us the emails" as she walks among protesters chanting "show us your taxes" outside the Charlotte Convention Center. (Gerald Herbert/Associated Press)

Danielle Allen is a political theorist at Harvard University and a contributing columnist for The Post.

Abraham Lincoln is said to have offered one of the sharpest, smartest defenses of the intelligence of a democratic people I’ve ever seen: “You may fool all the people some of the time; you can even fool some of the people all the time; but you can’t fool all of the people all the time.” In short, we’re smarter together.

But that’s not what the Trumps think.

Donald Trump's stance on presidential candidates has changed significantly over the years. Here's how. (Peter Stevenson/The Washington Post)

Eric Trump thinks his dad shouldn’t release his taxes because then there would be “a bunch of people who know nothing about taxes trying to look through and trying to come up with assumptions on things they know nothing about.”

Well, I’m sure it’s true that out here among us little people in the great beyond of non-billionaire-land, there are some who know very little about taxes and who couldn’t do much with Donald Trump’s returns, but there are also an awful lot of us for whom taxes are a part of a lifelong adult learning curriculum that even brings an excruciating, annual deep-dive refresher course. And then there’s a not insignificant number of true experts who would surely be willing to leaven our collective intelligence to bring to a high level — even the highest — the accumulated sum of our efforts to analyze those truly amazing, surely stupendous, the likes of which ain’t never been seen before Trump tax returns.

The intelligence of the American people. I love it. Really. What all of us can do, together? It’s really something. The United States is great. No one can analyze a tax return like the American people. It’s true, Eric. We’re down with tax returns. So bring it on.

You say an audit blocks it? The IRS says that’s no hindrance. And anyway, the returns up to 2008 are out of audit. Let’s start with those.

The cat’s out of the bag, then. The Trumps have no respect for the intelligence of the American people. Not that the cat was ever terribly well hidden. Trump has ignored not only Lincoln’s maxim but also another one that goes something like this: “You can amuse all of America some of the time, and some of America all of the time (by invoking, whenever folks get bored, the Great Wall of Trumplandia). But it turns out you can’t amuse all of America all of the time.”

For instance, Trump’s audience for “The Apprentice” included many African Americans, but his poll numbers don’t. A common explanation for this is that Trump alienated those erstwhile fans when he became the leading advocate for the birther movement, helping to drive the president of the United States to release his long-form birth certificate.

Trump’s advocacy for the release of Obama’s birth certificate is worth probing. The idiotic conspiracy theory was not hard to see through, yet a stunning number of Americans went along with it. And now, despite having pushed to excess for transparency in that case, Trump expects us not to notice, or to disregard, his own refusal to meet a basic norm of transparency. He is dragging our intelligence through the mud.

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So maybe this is one reason most African Americans don’t plan to vote for Trump. Because you know what? African Americans are exceptionally good at registering when someone has no respect for our intelligence. We’ve had a fair amount of practice. Take Trump’s new campaign manager, Kellyanne Conway, for example. In a recent interview on the ABC’s “This Week,” she said this about New York City charter schools serving African American and Hispanic American students: “It’s just remarkable to see the quality education that these students who are fully capable and very intelligent receive through school choice and charters.” Why is Conway explicit about the students’ abilities? Her language reveals that she imagines an audience that doesn’t necessarily believe in the intelligence of African Americans and Hispanic students. An audience with such a starting point will hear her comment one way, but an audience of African Americans or Hispanics who do indeed take their own intelligence for granted will hear her in quite a different way.

Certainly, for many moons now, and some would say for years, Trump has made clear his disrespect for the intelligence of African Americans. His current strategy of talking “at” not “to” African Americans, to quote Rep. G.K. Butterfield (D-N.C.), is but the latest example of a consistent pattern. But this is also a case in which African Americans are, once again, and perhaps most importantly, the miners’ canary.

African Americans may have noticed it first, but the truth is that Trump doesn’t respect anyone’s intelligence. The ever more elaborately embellished castle in the air that is Trump’s great wall — as of this week it will have protections against tunnels — is a particularly vivid example of how throughout this campaign he has displayed his disrespect for the intelligence of the American people.

Eric Trump is simply giving voice to what all along has been the script. It would be “foolish,” as he put it, for the Trumps to frame their decisions by presuming they can have confidence in Americans’ brains.

By now, most of us are not fooled. By now, most of us are not amused. We’ll see whether it stays that way. Seventy-odd days to go. May this great people once again prove Lincoln right.