But by endorsing legal immigration cuts, a move he has long supported, Mr. Trump returned to a theme that has defined his short political career and excites his conservative base at a time when his poll numbers continue to sink. Just 33 percent of Americans approved of his performance in the latest Quinnipiac University survey, the lowest rating of his presidency, and down from 40 percent a month ago.
Democrats and some Republicans quickly criticized the move. âInstead of catching criminals, Trump wants to tear apart communities and punish immigrant families that are making valuable contributions to our economy,â said Tom Perez, the chairman of the Democratic National Committee. âThatâs not what America stands for.â
The bill, sponsored by Senators Tom Cotton of Arkansas and David Perdue of Georgia, would institute a merit-based system to determine who is admitted to the country and granted legal residency green cards, favoring applicants based on skills, education and language ability rather than relations with people already here. The proposal revives an idea included in broader immigration legislation supported by President George W. Bush that died in 2007.
More than one million people are granted legal residency each year, and the proposal would reduce that by 41 percent in its first year and 50 percent by its 10th year, according to projections cited by its sponsors. The reductions would come largely from those brought in through family connections. The number of immigrants granted legal residency on the basis of job skills, about 140,000, would remain roughly the same.
Under the current system, most legal immigrants are admitted to the United States based on family ties. American citizens can sponsor spouses, parents and minor children for an unrestricted number of visas, while siblings and adult children are given preferences for a limited number of visas available to them. Legal permanent residents holding green cards can also sponsor spouses and children.
In 2014, 64 percent of immigrants admitted with legal residency were immediate relatives of American citizens or sponsored by family members. Just 15 percent entered through employment-based preferences, according to the Migration Policy Institute, an independent research organization. But that does not mean that those who came in on family ties were necessarily low skilled or uneducated.
The legislation would award points based on education, ability to speak English, high-paying job offers, age, record of achievement and entrepreneurial initiative. But while it would still allow spouses and minor children of Americans and legal residents to come in, it would eliminate preferences for other relatives, like siblings and adult children. The bill would create a renewable temporary visa for older-adult parents who come for caretaking purposes.
The legislation would limit refugees offered permanent residency to 50,000 a year and eliminate a diversity visa lottery that the sponsors said does not promote diversity. The senators said their bill was meant to emulate systems in Canada and Australia.
The projections cited by the sponsors said legal immigration would decrease to 637,960 after a year and to 539,958 after a decade.
âOur current system does not work,â Mr. Perdue said. âIt keeps America from being competitive and it does not meet the needs of our economy today.â
Mr. Cotton said low-skilled immigrants pushed down wages for those who worked with their hands. âFor some people, they may think that thatâs a symbol of Americaâs virtue and generosity,â he said. âI think itâs a symbol that weâre not committed to working-class Americans, and we need to change that.â
But Senator Lindsey Graham, Republican of South Carolina, noted that agriculture and tourism were his stateâs top two industries. âIf this proposal were to become law, it would be devastating to our stateâs economy, which relies on this immigrant work force,â he said. âHotels, restaurants, golf courses and farmers,â he added, âwill tell you this proposal to cut legal immigration in half would put their business in peril.â
Cutting legal immigration would make it harder for Mr. Trump to reach the stronger economic growth that he has promised. Bringing in more workers, especially during a time of low unemployment, increases the size of an economy. Critics said the plan would result in labor shortages, especially in lower-wage jobs that many Americans do not want.
The National Immigration Forum, an advocacy group, said the country was already facing a work force gap of 7.5 million jobs by 2020. âCutting legal immigration for the sake of cutting immigration would cause irreparable harm to the American worker and their family,â said Ali Noorani, the groupâs executive director.
Surveys show most Americans believe legal immigration benefits the country. In a Gallup poll in January, 41 percent of Americans were satisfied with the overall level of immigration, 11 percentage points higher than the year before and the highest since the question was first asked in 2001. Still, 53 percent of Americans remained dissatisfied.
The plan endorsed by Mr. Trump generated a fiery exchange at the White House briefing when Stephen Miller, the presidentâs policy adviser and a longtime advocate of immigration limits, defended the proposal. Pressed for statistics to back up claims that immigration was costing Americans jobs, he cited several studies that have been debated by experts.
âBut letâs also use common sense here, folks,â Mr. Miller said. âAt the end of the day, why do special interests want to bring in more low-skill workers?â
He rejected the argument that immigration policy should also be based on compassion. âMaybe itâs time we had compassion for American workers,â he said.
When a reporter read him some of the words from the Statue of Liberty â âGive me your tired, your poor, your huddled masses yearning to breathe freeâ â Mr. Miller dismissed them. âThe poem that youâre referring to was added later,â he said. âItâs not actually part of the original Statue of Liberty.â
He noted that in 1970, the United States allowed in only a third as many legal immigrants as it now does: âWas that violating or not violating the Statue of Liberty law of the land?â
An earlier version of this article misstated part of President Trump’s effort to stem the flow of immigrants into the United States. He has increased immigration arrests, not deportations.