“When someone shows you who they are, believe them the first time.”

Even if you’ve never read any of Maya Angelou’s books, even if you have no idea who the late author is, you know that quote. It’s the go-to “told you so” to admonish anyone surprised by terrible behavior from someone with a record of behaving terribly.

It’s the phrase women use to comfort the girlfriend who swore she could succeed in reforming her “bad boy” boyfriend when the relationship predictably crashes and burns.

And, in the time of Donald Trump and his march to the Republican presidential nomination and maybe back to the White House, it has been repeated so often, it’s cliché.

So why is the not-so-shocking realization that Trump means what he says about retribution and a coming dictatorship greeted with a shrug?

OK, that’s not strictly true.

A few saw the endgame from the time Trump morphed from reality TV star to politician. And now, a rash of articles and books are warning that he means exactly what he has been saying all along.

But for those just now seeing the malevolence behind the bluster, it sure took a long time and a genuine insurrection for the amusement to turn into disgust.

After Angelou’s words have proven true time and again, no sensible person should doubt her wisdom. Yet, many continue to make excuses, insisting that anyone who takes Trump’s words and record seriously is being ridiculous and that American voters need not take a closer look at the phony wizard behind the curtain.

Will an empowered President Trump yank the country out of NATO, blowing up longtime global alliances? Will he weaponize a Justice Department newly staffed with cronies like Jeffrey Clark, the attorney general-in-waiting whose desperate promotion as a means to keep Trump in office after his 2020 defeat was foiled only by threats of mass resignations? Will Trump obliterate the Constitution by imposing religious tests and demanding loyalty oaths to determine who is and is not truly “American”?

Kash Patel, a former Trump administration adviser who is likely to return if Trump does, was giddy when he announced plans to go after perceived enemies in the media with criminal and civil prosecutions. His friendly podcast interviewer was pardoned-but-hardly-chastened Steve Bannon.

Imagine what disgraced and pardoned former Lt. Gen. Michael Flynn unleashed would do. Might he reactivate his plan to send the military to run elections again — after voting machines that delivered the “wrong” result have been seized?

Jaw-dropping? Maybe only to some.

That’s the scary part.