Are President Obama, Hillary Clinton and violent leftists in cahoots to elect Donald Trump? Or are they just idiots?

The evidence is overwhelming that they all belong to a conspiracy — either of secret GOP sympathizers or of dunces. Those are the only options after Democrats took turns denouncing Trump in ways that actually bolstered the potency of his arguments. Three examples tell the tale.

First, Obama traveled to Indiana to deliver what aides called his first attempt to influence the election. That’s a lie, of course, but not the biggest one of the day. No. 1 would be Obama’s touting the economy as a roaring success.

“If what you care about in this election is your pocketbook; if what you’re concerned about is who will look out for the interests of working people and grow the middle class,” the president claimed, “if what you’re concerned about is the economy, then the debate is not even close.”

He crowed about “progress” made during his tenure, and said sticking with Democrats was the only sensible option.

Two days later, the Labor Department reported that employers added a mere 38,000 jobs in May, the worst report in six years. Even with massive help from the Federal Reserve, the economy’s slow growth means it has created three million fewer jobs than it should have by now, making Obama’s boast look ridiculous.

It also makes Trump’s focus on creating jobs and criticism of ­international trade deals look like the right ideas. After all, if puny growth for seven years is the best Obama can do, why not give the other team and other ideas a chance?

Clinton provided the second backfire example with her ­foreign-policy speech. It had very little to do with actual foreign policy, and everything to do with a rehearsed rant on Trump. She called him reckless, childish, uninformed and unprepared.

“This is not someone who should ever have the nuclear codes,” she declared.

The liberal press ate it up, displaying a remarkable talent for ignoring the foreign-policy ­disasters unfolding around the world, courtesy of Clinton and Obama. The next president will inherit the brutal aggressions of China and Russia and the cancerous spread of Islamic terrorism.

And it takes a special media willfulness to refuse to see the biblical deprivations befalling millions of refugees spilling out from Syria and Libya after Obama and Clinton helped turn those countries’ crises into ­catastrophes. In a recent span of just eight days, about 1,000 people drowned trying to escape across the Mediterranean to ­Europe.

If that’s the best Dems can do, why should they get a third term? Would Trump be worse?

The third evidence of a conspiracy involved a Trump rally in San Jose, Calif. Or rather, it ­involved the thugs, gang members and people burning the American flag and waving Mexican flags who attacked Trump supporters.

An ABC reporter tweeted that police lost control and that “Trump supporters [were] being terrorized and beaten up by mobs of protesters.” Among those beaten was a man named Juan Hernandez, a gay Latino Trump supporter who released photos of his broken nose and bloody shirt, along with a statement, writing:

“Got jumped last night as we exited the rally . . . Thanks for a broken nose, uncontrollable bleeding, and a bash to the head, Democrats. You sure are doing your party proud.”

As Hernandez notes, the violence helps make Trump’s case. If the candidate’s promise to control the border brings such a ferocious backlash, he’s on to something.

That scary thought must have seeped into the central brain of The New York Times, which gave a disgracefully distorted picture of what happened in San Jose. It called the one-way ­assaults “clashes” between “protesters” and Trump backers, as if both sides were equally to blame.

Even more shameful, the paper’s Friday article included this sentence: “While Mr. Trump has said he does not condone violence of any kind, his campaign made little effort to condemn it.”

You can’t be that ignorant without intent.

The pattern is obvious — the Democrats’ Way is in trouble. The economy won’t cooperate with their big-government nostrums, Clinton is dodging Bernie Sanders and the FBI, and Obama doesn’t understand why the world doesn’t treat his every ­utterance as gospel.

Maybe they should take a hint. Maybe, finally, America has had enough.

Violent schools’ math problem

How violent are New York City schools? Good question, but there’s no good answer.

A mishmash of conflicting data were revealed when parents, supported by charter groups, sued the city, saying there is so much crime that students are denied their right to a sound education. They point to state statistics gathered by schools that show a 23 percent increase in violent incidents last year.

But the city uses a different measurement compiled by the NYPD. It showed violent incidents declined slightly in the same period.

This is nuts. You can’t solve a problem if you can’t measure it.

Then again, maybe that’s the point. It’s easier for educrats to hide behind confusion rather than make schools safer. No news there, only tragedy as usual.

The Blas & Cuomo snipe fest

Tolstoy’s opening line in “Anna Karenina,” that “All happy families are alike; each unhappy family is unhappy in its own way,” also applies to political feuds. Witness the unhappy battle between New York’s top Democrats.

With federal prosecutors probing both Gov. Cuomo and Mayor de Blasio, the officials’ sniping at each other amounts to a shootout in a lifeboat. Even the survivor might not last long.

For his part, de Blasio is fixated on the least of his legal problems — a state Board of Elections report that accused him of “willful and flagrant violations” of campaign-finance laws. Repeatedly accusing Cuomo of orchestrating the report and leaking it to the press, he said it employed a double standard by ignoring Cuomo’s fund-raising.

Even when the leaker was identified as a Republican operative, de Blasio refused Cuomo’s demand for an apology, saying it’s “not going to happen.”

The governor, never one to turn the other cheek, had aides bombard de Blasio with mocking Twitter attacks. “I’m sure saying ‘I was wrong’ is one of the hardest things to do in politics, but continuing this charade at this point is just silly,” a Cuomo spokesman wrote. Later, he added that “Deflect is a lesser known river in Egypt as well.”

So far, there is no indication the twin federal investigations are linked, and de Blasio certainly looks to be in more personal hot water.

Still, the feds could use the feud to their advantage: Put both men under oath and get them to tell all they know about each other. That would be special.

A key difference between Trump and Obama

Reacting to my column that Donald Trump and President Obama are “two sides of the same coin,” reader Charles Parham begs to differ, writing: “Trump loves the country, Obama loathes it.”