President Trump has endorsed legislation that would slash legal immigration by half, mainly by cutting the number of visas granted to relatives of citizens, while favoring people who speak English and have advanced degrees. The bill, which would do nothing to solve the country’s immigration and economic challenges, is unlikely to become law. The only way to understand Mr. Trump’s vocal support of an obvious turkey is as yet another attempt to energize his dwindling base of right-wing and nativist supporters.

The bill was introduced by two Republican senators, Tom Cotton of Arkansas and David Perdue of Georgia, who say it will protect American workers from competition from low-skilled foreign workers. Right now, the government issues more than a million green cards every year, most of them to relatives of citizens. A smaller number, 140,000, are provided on the basis of job skills.

The proposal would slash the total number of green cards issued by 41 percent in the first year and by 50 percent in the 10th year, with most of the cuts coming from family-based immigration. It would cap the number of refugees admitted every year and eliminate a program that provides green cards via lottery to people from countries that send few immigrants to the United States. The bill would not reduce employment-based green cards, but it would change how the recipients are selected by putting in place a points-based system that rewards people who speak English and have advanced degrees and work experience.

The issue of immigration in America is volatile and complex and thus vulnerable to seductive promises. This bill falls into that category. Its central premise — that it would help American workers — is false. It’s true that an influx of workers can cause short-term disruptions to the labor market, but the impact on the wages of native workers over a period of 10 years or more is “very small,” according to a comprehensive National Academies of Sciences, Engineering and Medicine report published last year.