The major potential threats from a Kamala Harris or a second Donald Trump administration could range from a continuation of governance as usual to catastrophe. Thus, my criteria for choosing the worst policy must meet these three criteria:

  1. The policy is solely within the president’s ability to enact,
  2. The candidate has either attempted, supported, or accomplished the policy before, and
  3. The policy would impose enormous economic and social costs on the United States.

Considering those three features of potential policies, my biggest concern is that a second Trump administration will practically end legal immigration to the U.S. The Supreme Court ruled in its 2018 Trump v. Hawaii decision that the president can restrict legal immigration in whatever way he wishes so long as he uses “national security” as justification.

Furthermore, the Trump administration learned how fragile the legal immigration system is during the pandemic. Multiple government agencies, including the State Department, Department of Homeland Security, Department of Labor, Department of Agriculture, and others are involved in visa approvals and issuances for applicants overseas. Obstructing the operations of one or all those departments is all that’s required to stop visa issuances and applicants overseas have effectively no legal recourse—but they could always attempt to immigrate illegally.

Domestic visa applicants, such as the many millions on temporary visas who desire and are eligible for green cards, have more recourse and they would be less obstructed. It took over a year for visa processing at U.S. embassies to recover after the brief shutdown during the pandemic. If enacted early in the second Trump administration, it would take even longer for the legal immigration system to recover after four years of clinical death.

There’s every reason to believe that President Trump would massively restrict legal immigration and could essentially end it, with a likely exception for temporary lower-skilled agricultural workers. Trump reduced legal immigration during his first administration, even before the pandemic, when he virtually ended it entirely except for low-skilled temporary farm workers. He has not changed his mind since then.

Such policies ignore that immigrants are enormously economically beneficial. They increase the supply and demand sides of the economy, expanding production and consuming goods and services produced by others. They account for most of the growth in the workforce and are almost twice as likely to start a business. They are almost 50 percent more likely to patent, more likely to work, and they generally pay more in taxes than they receive in government benefits. For instance, new research from the Congressional Budget Office estimates that the recent surge of immigration into the U.S. will reduce deficit spending by almost $900 billion over the next decade.

But the president has the power to unilaterally restrict legal immigration by vague appeals to national security. President Trump did it before and there’s evidence he’d try it again.