What’s a fear-based demagogue to do?

It was a bad day for President Fear and the folks at Fox News.

They had planned jointly to set pheromones aflame with high-decibel sounds about a caravan of people headed to our borders from Honduras.

Oh, my: people in brown skin coming to do terrible things — clean toilet stalls, change hotel bed sheets, replace shingles on blistering roofs, and otherwise breathe free. The horror.

Then what should happen but a succession of events to pre-empt all that airwave froth that Fox and the president wanted viewers to hear and fear.

It came in the mail — bombs sent to select critics of the president, including two former presidents.

Trump acolytes like Fox News’ Lou Dobbs and Rush Limbaugh trotted out a “false flag” theory (1) these weren’t bombs; (2) a liberal or liberals had mailed them to discredit Donald Trump and his flock.

This theory hinged on the notion that the law enforcement agencies, from federal to local, were all in on the ruse. Now, that’s one massive ruse. It takes that whole “deep state” claim from quaint and comical all the way to Rocky and Bullwinkle.

Then came an arrest: mid-day — a news-cycle disaster. And with it came the most searchable term imaginable: the MAGA Bomber.

So sad. Without exacting so much as a pound of actual liberal flesh, red-capped Cesar Sayoc had blown up a whole, fertile weekday news cycle, or seven.

Fox News, in full pout, reported these facts. It did, however, blur out the fawning portrait of Trump and the targets drawn on the images of Hillary Clinton and Michael Moore on the suspect’s van.

Then a shooter took three handguns and an assault rifle and methodically killed 11 people at a Pittsburgh synagogue. He’d spewed his venom all over social media first, introducing non-extremists to Gab, which prides itself on providing a megaphone to anyone to say anything freely.

What had fueled Robert Bowers’ hatred? For one, those Trumpian warnings about refugees from Central America and Bowers’ belief that a Jewish advocacy group was promoting it.

Like our president, Bowers used the word “invaders” to describe the dark-skinned travelers.

Who wouldn’t be alarmed by the Trump-beat about that caravan? After all, our president warned that there might be “Middle-Easterners” in the bedraggled throng. Then it was violent gang members.

Let’s face it. If the package comes in certain pastels, the official policy of this administration is to send the military.

Submerged in all this was the tragedy in Jeffersontown, Ky., in which a white gunman who couldn’t get inside a predominantly black church to kill people went to a nearby grocery store and killed two black people.

So, tell us what pastel to fear, Mr. President.

This president is biologically adverse to anything that doesn’t fit his prejudices, with a supporting throng that bolsters what he hates.

In light of the mailing of bombs, Trump robotically called “terrorizing acts despicable.” He called for civility, then, refusing to cancel an appearance on a stage provided by the enemy of the people, skipped out onto the campaign trail to return to his divisive self, his raving supporters denouncing his opponents as mobs.

Trump knows how he won the presidency: by appealing to a constituency just narrow enough to get the electors he needed. He apparently has realized that he cannot attract a broader base, so he has sought, with every word and gesture, to harden the base he has.

He said, “No nation can succeed that tolerates violence or the threat of violence as a method of political intimidation, coercion or control.”

Yet just days earlier he applauded Montana Congressman Greg Gianforte for “body-slamming” a reporter.

In light of these horrifying events, being the con man he has shown himself to be, Trump’s call for unity was every bit as sincere as flipping paper towels to Puerto Rico.

The headline on Michael Tomasky’s column in The Daily Beast said it all. In fact, it may be the most succinct summation of the Trump presidency:

“A president who hates half the country doesn’t get to call for unity.”