President Donald Trump is steering U.S. economic policy in a radically new direction. From trying to revive steelmakers with tariffs to vetoing Chinese technology investments, he is using the federal government to direct which industries prosper and which don’t.

Many countries have long tilted the playing field toward favored companies and industries, a practice economists call industrial policy. American presidents have traditionally resisted this as “picking winners.”

The president has broken with that tradition, unveiling a series of actions on trade, foreign investment and energy he hopes will revive favored industries and beat back the competitive challenge of other countries—but which risk creating domestic losers.

His administration pushed strongly for a bill Congress is about to pass significantly expanding Washington’s power to scrutinize foreign investment and transactions that could compromise U.S. technological leadership.

These aren’t easily labeled a single, coherent policy because they reflect a mix of motives: nostalgia for America’s past industrial greatness, devotion to Mr. Trump’s electoral base and deep suspicion of China. What they do share is a willingness to override private business and investor decisions in the interests of national security, as Mr. Trump defines it.