President Trump has reportedly told cabinet members that Elon Musk may soon leave the administration. If and when he goes, what will he leave behind?

Mr. Musk has long presented himself to the world as a futurist. Yet, notwithstanding the gadgets — the rockets and the robots and the Department of Government Efficiency Musketeers, carrying backpacks crammed with laptops, dreaming of replacing federal employees with large language models — few figures in public life are more shackled to the past.

On the day of Donald Trump’s inauguration, Mr. Musk told a roaring, jubilant crowd that the election marked “a fork in the road of human civilization.” He promised to “take DOGE to Mars” and pledged to give Americans reasons to look “forward to the future.”

In 1932, when civilization stood at another fork in the road, the United States chose liberal democracy, and Franklin Roosevelt, who promised “a new deal for the American people.” In his first 100 days, Mr. Roosevelt. signed 99 executive orders, and Congress passed more than 75 laws, beginning the work of rebuilding the country by establishing a series of government agencies to regulate the economy, provide jobs, aid the poor and construct public works.

Mr. Musk is attempting to go back to that fork and choose a different path. Much of what he has sought to dismantle, from antipoverty programs to national parks, have their origins in the New Deal. Mr. Roosevelt’s Works Progress Administration provided 8.5 million Americans with jobs; Mr. Musk has measured his achievement in the number of jobs he has eliminated.

Four years ago, I made a series for the BBC in which I located the origins of Mr. Musk’s strange sense of destiny in science fiction, some of it a century old. This year, revising the series, I was again struck at how little of what Mr. Musk proposes is new and by how many of his ideas about politics, governance and economics resemble those championed by his grandfather Joshua Haldeman, a cowboy, chiropractor, conspiracy theorist and amateur aviator known as the Flying Haldeman. Mr. Musk’s grandfather was also a flamboyant leader of the political movement known as technocracy.