What if Trump does what he’s saying he’ll do?

Donald Trump recently declared at a Virginia rally that if reelected as president he would not “give one penny to any school that has a vaccine mandate.” Trump did not acknowledge, or does not know, that all 50 states require public school students to be vaccinated for several diseases — including hepatitis A and B, diphtheria, tetanus, polio, chickenpox, varicella, measles, mumps and rubella (with exemptions often allowed for medical reasons and “reasons of conscience”).

Vaccination requirements have been extraordinarily effective in protecting the health of children, reaching “herd immunity” and saving millions of lives. 88 percent of Americans believe the benefits of these vaccines outweigh the risks.

Nevertheless, in an apparent attempt to appeal to anti-vaxxers and have it both ways, the former president repeated his promise several times, while a campaign spokesman (but not Trump) indicated he was referring only to Covid-19 mandates. Not surprisingly, then, Dr. Peter Hotez, an expert in infectious diseases, expressed the hope that Trump “doesn’t really mean it, since it would create a public health catastrophe for the nation.”

But what if Trump does mean it? What if Trump returns to the White House and does what he’s saying he’ll do about a host of vital issues?

Here are the real-world implications for a few of Trump’s tough-guy campaign promises.

Opposed to U.S. military assistance to Ukraine, Trump emphasizes he will “encourage” Russia “to do whatever the hell they want” to any NATO country that has not met the organization’s defense spending target of 2 percent of GDP. Trump doesn’t seem to care that failing to defend a NATO ally would violate America’s treaty obligations; weaken our national security; give a green light to dictators; and undermine deterrence, global political stability and the world economy.

Trump says he intends to impose a 10 percent tariff on all U.S. imports and phase out Chinese electronics, steel and pharmaceutical products. The tariff, he asserts, would “really make a lot of money.” Virtually every economist disagrees. The Tax Foundation, a conservative nonprofit, estimates that a 10 percent across-the-board tariff would reduce America’s GDP by 0.7 percent a year, eliminate about 500,000 jobs and increase inflation. If other nations retaliate, as they almost certainly would, another 0.4 percent would be shaved off GDP and an additional 322,000 jobs lost.

Emphasizing that immigrants “are poisoning the blood of our country,” Trump wants to ban travel from Muslim-majority countries to keep “radical Islamic terrorists” — and anyone who sympathizes with them — out of the U.S. He has pledged to shut down the U.S.-Mexico border on “day one” and reassign troops now deployed overseas to secure it.

Even if the soldiers succeed in turning back most or all migrants, by no means certain, a prolonged closure would wreak havoc with the American economy. Mexico is America’s largest trading partner. According to Jerry Pacheco of the nonprofit Border Industrial Association, millions of jobs “depend on the binational relationship.” Since 37 percent of imported parts used in U.S. vehicles come from Mexico, a shutdown would bring the automobile industry to a halt.

Trump is also planning “the largest domestic deportation operation in American history,” for which he claims he doesn’t need congressional approval. The massive operation would be aimed at about 11 million undocumented immigrants, 6 million of whom have lived in the United States for more than 10 years, some 39 percent of them born in Mexico. The immigrants would have to be identified, detained, processed through the legal system — where they retain some rights — and then transported abroad.

Trump also intends to issue an executive order withholding passports, Social Security numbers and other benefits from children of undocumented immigrants who were born in the United States — a blatant violation of birthright citizenship, which is guaranteed in the Constitution.

Since ICE employs only 6,000 deportation agents, active-duty service personnel and men and women in the National Guard would be deployed to round up the suspects, subdue anyone who resists arrest and run detention camps. It is not at all clear where the deportees and their children would be sent or whether their countries of origin would accept them.

The initiative would do massive damage to the economy. The labor force includes 9 million undocumented immigrants, who account for 10 percent of the total output in the agriculture, leisure and hospitality, and construction sectors, and who would be difficult, if not impossible, to replace.

According to an estimate made 10 years ago, deportation of all undocumented workers would shrink the labor force by 6.4 percent. When the costs of removal are included, GDP would decrease by trillions of dollars.

And deportation is virtually certain to tear the country apart, with millions of Americans resisting, perhaps violently.

Ahead of the 2024 Iowa Caucuses, Trump posted a video on Truth Social in which a narrator reveals that God had searched for someone “who can shape an axe but wield a sword … make money from the tar of the sand, turn liquid to gold, who understands the difference between tariffs and inflation.” God then anoints Trump as his shepherd, to drill for fossil fuels, create jobs, secure the southern border, strengthen the military and fight the system all day, but still find time to attend church on Sunday.

Meanwhile, Trump is laying plans to do what he is saying he’ll do.

Glenn C. Altschuler is the Thomas and Dorothy Litwin Emeritus Professor of American Studies at Cornell University.