“I alone can fix it,” said Donald Trump in 2016. Four years later, it’s clear he wasn’t talking about national unity, race relations, public health, deficit spending or decaying infrastructure. Maybe he meant the coal industry.

No sector of the economy received more love from candidate Trump than the producers of “beautiful, clean coal.” His mass rallies almost invariably included paeans to these victims of supposed climate-change lunacy, and his audiences cheered his promise to restore coal mining to its former glory as the fossil fuel of choice for the generation of electricity.

Four years later, let’s see how Mr. Fix-It is doing with coal.

Peabody (formerly Peabody Energy) is by far the largest coal producer in the United States, according to the federal Energy Information Administration. With mines throughout the country, the company suffered under the anti-coal policies of the Obama administration and entered bankruptcy in 2016. Trump was speaking Peabody’s language when he pledged to end “the war on coal.” Under the new administration, the reorganized company roared out of bankruptcy and back into the Fortune 500.

Initially, things looked good. By June 2018, Peabody’s stock was selling for nearly $47 per share. But now that Trump has had more time to work his magic, Peabody is hemorrhaging, and its share price has plunged to less than $3.50.

Arch Coal is the next largest outfit, with 13 percent of the U.S. market in 2018. Its share price has fared better than Peabody’s, despite losing more than 60 percent of its value during Trump’s time in office.

The No. 3 and No. 4 producers in the EIA rankings, Cloud Peak Energy and Murray Energy, are both in bankruptcy. Fifth on the list is Alliance Resource Partners (ARP), headquartered in Tulsa, where Trump plans to hold his first covid-era rally on June 19. ARP chief executive Joe Craft is a product of impoverished Eastern Kentucky who bootstrapped his way into the billionaire class. He donated $1 million for the Trump inauguration festivities, and his wife, Kelly Craft, is now U.S. ambassador to the United Nations.

Craft’s company has not fared well, either.

Six years into the Obama administration, a share of Alliance Resource stock cost nearly $50. By the time Trump took office, the price had fallen by half. No wonder Craft chipped in for a celebration. Help was on the way, right?

Wrong. Despite Trump’s love for coal and his self-proclaimed hypercompetence, Craft’s company’s stock now sells for around four bucks per share.

The collapse of coal is not exclusively Trump’s doing. It is the result of abundant natural gas and changing consumer priorities among carbon-conscious Americans. Power companies continue to shutter their coal-fired plants because, as one utility executive told me, “our customers don’t want it.” Ten years ago, coal generated more than half of America’s electricity; today, coal accounts for about one-fifth — and falling. The fastest-growing electricity source is wind.

But Trump pledged to change all that; thus coal is emblematic of the president’s executive fecklessness. Though numerous as stars in the night sky, Trump’s words are hollow. When it comes to promises, Trump is full of something, but it’s not results.

There is no wall along the southern border. Having promised to build 450 miles of new barrier by November, he’s already far behind schedule. The relatively short stretch he has managed to build is not impenetrable, as Trump promised. According to Customs and Border Patrol records, obtained by The Post’s Nick Miroff, the Trump barrier is so easily breached that, during one month last fall, smugglers cut 18 holes in a single stretch.

And no, Mexico hasn’t paid a peso for construction, despite Trump’s incessant campaign promises. The president found the money the same place he goes to fund most of his pet projects: our grandchildren’s pockets. Having boasted that he could balance the budget “relatively quickly,” Trump has engaged in an orgy of deficit spending.

He promised extraordinary economic growth. When primary opponent Jeb Bush promised a 4 percent growth rate, candidate Trump offered “five or even six.” In fact, his best annual performance has been 2.9 percent. Currently, he’s presiding over the deepest crash since the Great Depression.

“America will never bow to a foreign nation,” Trump promised — but he groveled after the crown prince of Saudi Arabia rather than insist on justice after the murder of Jamal Khashoggi. He abandoned the Kurds in Syria to Turkey’s Recep Tayyip Erdogan. Cutting U.S. forces in Germany is his latest kowtow to Russian President Vladimir Putin.

Trump hasn’t delivered a China trade deal. He hasn’t delivered a denuclearized North Korea. He hasn’t delivered Middle East peace. As for making America great again — his signature campaign promise — two-thirds or more of registered voters now believe that the nation is on the wrong track.

What can voters say, given such a performance? How about: “You’re fired.”

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