WASHINGTON — After years of high-profile debates over a border wall and a path to citizenship, the biggest obstacle to a bipartisan deal on DACA is quickly becoming legal immigration, an issue on which President Donald Trump has presided over a monumental shift in the GOP's approach.

Both sides have given ground elsewhere. A new proposal by the White House on Thursday would cede significant ground by offering a path to citizenship for all "Dreamers," which could include up to 1.8 million people brought to the United States illegally as children, not just those who have applied under DACA. The proposal also seeks $25 billion for a wall on the southern border, which Democrats (at least briefly) had already suggested they would fund to a substantial degree.

On legal immigration, though, the latest White House proposal puts them miles apart. It reflects a fundamental and growing ideological divide between Democrats and many Republicans who view immigration as a net good and Trump and his allies, who have depicted immigrants as an unwanted burden and threatening presence.

The White House is currently demanding that a deal on DACA recipients eliminate the diversity visa lottery — which issues 50,000 green cards a year in countries with few immigrants to the United States — along with family immigration categories for siblings and parents.

While some of the visas eliminated in the White House plan would go to clearing current backlogs of green card applications, immigration advocates say the long term effects are likely similar to hardline proposals in the House and Senate that would reduce overall immigration by 40 to 50 percent.

Sens. David Perdue, R-Ga., and Tom Cotton, R-Ark., who have a White House-backed bill of their own that would cut legal immigration by up to half, quickly endorsed the plan.

In an interview with CNBC that aired Friday morning, Trump, predicting success on a broader deal, praised the two senators as “great people” who have “really shifted a lot.”

“And I think they're willing to shift more, and so am I,” he said. “These are people that have very strong opinions on DACA and on immigration generally. And I happen to think they're largely right.”

Democratic leaders, including Dick Durbin of Illinois, the Senate minority whip, and Minority Leader Nancy Pelosi of California, however, quickly ruled it dead on arrival, with both citing its legal immigration provisions.

Cristina Jimenez, co-founder of the Dreamer advocacy group United We Dream, rejected the White House's proposal as a "nativist wish list" even as it moved the administration closer to activists' demands for a path to citizenship.

Republicans and Democrats working on an immigration deal have warned that taking up legal immigration and other issues was a likely deal breaker. The Trump proposal threatens to blow up those negotiations just as they begin.

“This should be a more narrowly focused discussion,” Sen. Angus King, I-Maine told NBC News on Monday. “To me, the logic has always been DACA and border security.”

Sen. Chuck Schumer, D-N.Y., the Senate minority leader, said in a floor speech on Thursday morning that Republicans could not get a deal by demanding a "vast curtailment of legal immigration," which he likened to Democrats demanding a path to citizenship for all 11 million undocumented immigrants in a DACA fix.

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On the other side, Sen. John Thune of South Dakota, a member of GOP leadership, also told reporters that "narrower gets it done," according to Politico.

“Legal immigration, broader chain migration reform, TPS, asylum policy, unaccompanied minors — those kind of things are going to have to be round two,” Sen. Jeff Flake, R-Ariz., told NBC News on Monday. “We can’t deal with all of them.”

A fundamental divide

The GOP demands fit a broader campaign spearheaded by Trump. From reportedly deriding immigrants from “shithole countries” in private to publicly backing major cuts to green cards and planning to expel longtime U.S. residents originally from El Salvador and Haiti, the president has pursued policies that would remove foreign nationals in America and reduce the number who might come in the future.

“It’s probably why it’s turned into such a standoff,” said Andrew Selee, president of the nonpartisan Migration Policy Institute. “This started out as a fairly noncontroversial trade-off between a very defined set of legal rights for a very defined population in return for border security spending, but it became a fight about much bigger immigration issues.”

Trump has denounced America’s immigrant communities in personal and false terms, telling supporters that these groups represent “the worst of the worst” and that foreign governments conspire behind the scenes to send them to the United States. In fact, potential immigrants apply individually and have to meet State Department requirements on work and education while passing background checks.

The White House has demanded that a bill address “chain migration" in favor of a more skills-based approach, but "chain migration" is a vague term. Many pro-immigration lawmakers have, like Trump, previously backed ending some family visa categories in favor of a new system that emphasizes economic needs and education.

But the real split is on total levels of immigration, which is where the two sides' competing visions express themselves clearly.

The leading Republican DACA bill in the House, the Securing America’s Future Act, would cut it by 38 percent, according to a report by the pro-immigration CATO Institute. The Trump-backed RAISE Act, co-sponsored by Perdue and Cotton, would reduce it by 43 percent.

“It’s not the method of how immigrants come in. It’s how many come in that’s the real problem,” said David Bier, who helped write the CATO report.

Bier said the White House plan would likely have a substantially similar effect on legal immigration as the two existing GOP-only bills.

A ‘remarkable’ shift

Republican leaders have mostly backed Trump’s demands in principle, and his plan on Thursday earned plaudits from even some relative moderates in the Senate while Speaker Paul Ryan and Senate Majority Leader Mitch McConnell issued noncommittal statements.

This is itself a major achievement for the movement Trump's administration has channeled in the White House.

“It’s remarkable we’re actually debating this question now, and this would not be happening without Trump’s election,” said Mark Krikorian, executive director of the Center for Immigration Studies, which advocates for fewer immigrants.

In previous years, prominent Republican leaders accepted the premise that legal immigration benefited America while promising to crack down on illegal immigration. Much of the argument was economic: Immigrants start businesses at high rates, pay taxes and raise children. Without them, America would suffer from population decline, economic stagnation and larger deficits.

With few exceptions, like Jeff Sessions, then a Republican senator from Alabama, and his then-aide Stephen Miller, the most prominent objections to the 2013 "Gang of Eight" bill concerned illegal immigration — even though it included major provisions expanding work visas and reorganizing immigration categories. Some high-profile conservatives who voted against the bill even complained it didn’t bring in enough foreign workers: Sen. Ted Cruz, R-Texas, offered an amendment to increase the number of H1B visas available by 500 percent.

But even before Trump’s election following a campaign rooted in anti-immigrant attacks, Republicans were moving to the right on the issue. Presidential candidates like Rick Santorum and Scott Walker linked immigration to lower wages. Meanwhile, Cruz disavowed his earlier position during the 2016 race and proposed a freeze on immigration levels until the economy improved.

Today Sessions and Miller are in the White House, and the transformation is complete.

A fight over limits

Immigration doves say they’re willing to address the issues the president named, but their approach is likely to be less far-reaching. The Durbin-Graham proposal that the White House rejected would have cut the diversity lottery, for example, but transferred its visas elsewhere and used some for similar purposes.

Immigration supporters argue that the family-versus-skills divide is overstated and that reunification should still be an important goal. Newly arrived immigrants are already more likely to have a college degree than native-born Americans, according to Pew Research, including the African immigrants Trump reportedly criticized in a recent White House meeting.

Those who support immigration are also suspicious that "merit" has much to do with Trump's actual goals. He reportedly told lawmakers he'd like to promote immigration from countries like Norway at the expense of countries in Africa, rhetoric that resembles ethnic nationalism more than any kind of individual meritocracy.

"The White House is using Dreamers to mask their underlying xenophobic, isolationist and un-American policies," Rep. Michelle Lujan Grisham, D-N.M., chair of the Congressional Hispanic Caucus, said in a statement Thursday.

The Trump framework may not go far enough for groups like NumbersUSA that want to reduce all immigration — but the plan, like the administration proposing it, would still pull immigration policy further in their direction than any bill in decades.