If basic civics was still taught, and required, for high school graduation, Trump could not claim that judges “sign bills.”

The dumbing down of this democracy has been gradual, and then — this year — all at once. The Princeton Review found that the Lincoln-Douglas debates of 1858 were engaged at roughly a high school senior level. A century later, the presidential debate of 1960 was a notch below, at a 10th grade level. By the year 2000, the two contenders were speaking like sixth graders. And in the upcoming debates — “Crooked Hillary” against “Don the Con” — we’ll be lucky to get beyond preschool potty talk.

How did this happen, when the populace was so less educated in the days when most families didn’t even have an indoor potty to talk about? You can look at one calculated loop of misinformation over the last two weeks to find some of the answer.

A big political lie often starts on the Drudge Report, home of Obama-as-Muslim stories. He jump-started a recent smear with pictures of Hillary Clinton losing her balance — proof that something was very wrong with her. Fox News then went big with it, using the Trump adviser and free-media enabler Sean Hannity as the village gossip. Then Rudy Giuliani, the internet diagnostician, urged people to Google “Hillary Clinton illness” for evidence of her malady. This forced Clinton to prove her stamina, in an appearance on Jimmy Kimmel, by opening a jar of pickles.

The only good thing to come out of this is that now, when you Google “Hillary Clinton illness” what pops up are scathing stories about a skeletal-faced rumormonger named Rudy Giuliani, and a terrific Stephen Colbert takedown of this awful man.

But what you don’t know really can hurt you. Last year was the hottest on record. And the July just passed was earth’s warmest month in the modern era. Still, Gallup found that 45 percent of Republicans don’t believe the temperature. We’re not talking about doubt over whether the latest spike was human-caused — they don’t accept the numbers, from all those lying meteorologists.