We have a word for people who are dominated by fear. We call them cowards. Trump was not a coward in the business or campaign worlds. He could take on enormous debt and had the audacity to appear at televised national debates with no clue what he was talking about. But as president his is a policy of cowardice. On every front, he wants to shrink the country into a shell.

J.R.R. Tolkien once wrote, “A man that flies from his fear may find that he has only taken a shortcut to meet it.”

Desperate to be liked, Trump adopts a combative attitude that makes him unlikable. Terrified of Mexican criminals, he wants to build a wall that will actually lock in more undocumented aliens than it will keep out. Terrified of Muslim terrorists, he embraces the torture policies guaranteed to mobilize terrorists. Terrified that American business can’t compete with Asian business, he closes off a trade deal that would have boosted annual real incomes in the United States by $131 billion, or 0.5 percent of G.D.P. Terrified of Mexican competition, he considers slapping a 20 percent tariff on Mexican goods, even though U.S. exports to Mexico have increased 97 percent since 2005.

Trump has changed the way the Republican Party sees the world. Republicans used to have a basic faith in the dynamism and openness of the free market. Now the party fears openness and competition.

In the summer of 2015, according to a Pew Research Center poll, Republicans said free trade deals had been good for the country by 51 to 39 percent. By the summer of 2016, Republicans said those deals had been bad for America by 61 percent to 32 percent.

It’s not that the deals had changed, or reality. It was that Donald Trump became the Republican nominee and his dark fearfulness became the party’s dark fearfulness. In this case fear is not a reaction to the world. It is a way of seeing the world. It propels your reactions to the world.