A coal miner shakes hands with President Trump in the White House on Feb. 16, 2017. (Ron Sachs/Pool/European Pressphoto Agency)

REPUBLICANS ACCUSED President Barack Obama of being a socialist. Yet President Trump is preparing what could be the most astonishing and counterproductive instance of central planning the nation has seen in decades.

Mr. Trump last Friday ordered Energy Secretary Rick Perry to recommend ways to prop up struggling coal and nuclear power plants. Mr. Perry’s previous attempt at doing so was practically laughed out of the Federal Energy Regulatory Commission, which unanimously rejected the notion that the U.S. power grid is at risk as clunker coal plants lose out to cheaper natural gas and renewables. But now the Trump administration is preparing more drastic alternatives.

One option would require the purchase of electricity from coal and nuclear plants under a law meant to keep power flowing during emergencies, such as hurricanes. Another scheme would hijack the 1950 Defense Production Act, which allows presidential intervention to secure critical goods when national security is at stake.

In either case, there would be many immediate losers. Americans could pay hundreds of millions, and perhaps billions, more every year for energy. Wholesale electricity markets could collapse as efficient power plants failed to compete with subsidized dinosaurs. People who live next to coal plants could continue to suffer from the health effects of the facilities’ noxious pollution. And the United States could pump out more planet-warming greenhouse-gas emissions.

There is a decent case for states to save nuclear power plants, which produce no dangerous air pollution, but not with such a massive government intervention such as the one the Trump administration contemplates. And there is no case for saving coal, an exceptionally dirty power source that should be retired as soon as possible.

If Mr. Trump proceeds and the courts somehow allow such a perversion of the law, it would be hard to stop the next Democratic president from, say, using emergency powers to force the purchase of renewables at the expense of coal, oil and natural gas.

The president’s latest turn toward economic statism should be no surprise; it has been an animating principle of his presidency. Mr. Trump entered office bullying individual companies, such as Carrier, into changing where and how they invest their money. He has since tried to use the power of his office to punish specific firms he dislikes, such as Amazon, whose founder and chief executive, Jeffrey P. Bezos, owns The Post. Mr. Trump is in the midst of picking unnecessary and increasingly costly trade fights with once-close allies, while assuring U.S. farmers that he will use state power — and, presumably, everyone else’s tax dollars — to preserve their margins. Now he is on the verge of asserting dictatorial control over energy markets, using powers meant to be reserved for real emergencies.

The only discernible emergency in this case is that Mr. Trump promised coal country a return to prosperity, which, because of coal’s cost and air pollution, the market will not provide. So the president may use the heavy hand of the state to force Americans to buy coal power, raising energy prices, in order to subsidize a narrow political constituency.