The most contentious piece of President Donald Trump’s new proposal to protect the so-called Dreamers has nothing to do with them. It’s the plan’s potential impact on legal immigration that sparked fierce Democratic opposition Friday and appeared to sink chances for a bipartisan deal in Congress.

The proposal outlined Thursday by the White House would end much family-based immigration and the visa lottery program, moves that some experts estimate could cut legal immigration into the United States nearly in half.

The plan would protect some 700,000 young immigrants from deportation and provide a pathway to citizenship, an offer the White House described as a concession to Democrats. But it also represented a victory for immigration hawks and a seismic shift for immigration policy in the U.S., which has long centered on the question of how to stop illegal border crossings, not how to curb legal immigration.

“It’s an enormous change in rhetoric and position,” said Alex Nowrasteh of the conservative Cato Institute. “Forever, people have talked about illegal immigration and now this anti-legal immigration position is standard for much of the Republican Party.”

The Senate’s top Democrat, Chuck Schumer of New York, dismissed the plan Friday as a “wish list” for hard-liners. He acknowledged the bipartisan common ground on protections for the immigrants now shielded by the Deferred Action for Childhood Arrivals program, or DACA. But he accused Trump of using them as “a tool to tear apart our legal immigration system and adopt the wish list that anti-immigration hardliners have advocated for years.”