DURING his presidential campaign, Donald Trump vowed to construct a wall along America’s southern border with Mexico to curtail illegal immigration. He often gave one caveat: this “big, beautiful wall” would have a “big, beautiful door” for those entering the country lawfully. Now, though, fellow Republicans have begun arguing that the door for legal immigrants should be made smaller.

There are two main paths for immigrants to become legal permanent residents in America: work and family. A new bill called the Reforming American Immigration for Strong Employment (RAISE) Act, proposed by two Republican senators, Tom Cotton of Arkansas and David Perdue of Georgia, would restrict the family route, which is sometimes referred to as “chain” migration. Unveiled on February 7th, the bill would allow legal permanent residents to sponsor their spouses or children under 18 for residency, but not more distant or adult relatives, as green-card holders can now. It would also cap the number of refugees offered residency at 50,000 a year and stamp out the diversity lottery, which distributes 50,000 visas a year to people from countries that have low rates of immigration to America.

Proud to become an American From 1990 to 2015 an average of 1m people became legal residents each year in America—up from an average of 532,000 between 1965 and 1990 (see chart). According to the Migration Policy Institute, during the past decade between 60% and 70% of lawful permanent immigration has been family-based. Messrs Cotton and Perdue estimate that the RAISE Act would reduce the number of legal immigrants by nearly 40% in its first year and 50% by its tenth year. Doing so, according to Mr Cotton, would promote higher wages for “all working Americans—whether your family came over here on the Mayflower or you just took the oath of citizenship.” Roy Beck, the founder of NumbersUSA, a group that advocates reduced immigration, applauds the bill, which he says will allow the labour market to tighten. He says dry-wallers, roofers and other low-skilled workers frequently write to him complaining that they were edged out of work by immigrants willing to accept lower wages. Critics say there is no evidence that immigration harms native-born workers on the whole, and studies show that immigration has a positive effect on labour-market outcomes in the long term. To that Mr Cotton responds: “Only an intellectual could believe something so stupid. The laws of supply and demand have not been magically suspended.”

The notion of curtailing legal immigration has lurched in and out of mainstream political debate in America for the past century. It was popular in the 1920s, in the wake of an earlier surge in immigrant flows, and inspired the enactment of two restrictive laws: the Emergency Quota Act of 1921 and the Immigration Act of 1924, which together established a quota system based on national origins. Another effort to reduce legal immigration came in the 1990s, after three decades of elevated immigration. In 1995 Bill Clinton initially endorsed a bipartisan congressional commission’s suggestion to slash legal immigration by a third, but the push for a law that would have cut family-chain migration failed after Mr Clinton withdrew his support.

The RAISE Act is also unlikely to prevail; two prominent Republican senators, Lindsey Graham and John McCain, have expressed opposition to it, along with their Democratic colleagues. But even if the legislation flops, the ideas it promotes will have powerful advocates in Washington. Jeff Sessions, Mr Trump’s attorney-general, has long championed reduced immigration. Stephen Miller, who was once Mr Sessions’s communications director and now advises Mr Trump, seems to share his old boss’s attitudes. Mr Trump’s own rhetoric on legal immigration is ambivalent. He has both called for the “big, beautiful door” and, in a policy speech before the election, said he wants “to keep immigration levels measured by population share within historical norms.”