President Trump may have hoped to increase pressure on congressional Democrats to accept other hardline elements of his immigration agenda this week by rescinding the program that has protected from deportation about 800,000 “Dreamers,” young people brought to the country illegally by their parents.

But it’s more likely Trump has triggered a process that will divide Republicans, further estrange him from the business community, and ultimately paralyze Congress, placing the issue of how to handle the “Dreamers” squarely back on his desk when his six-month deadline expires.

Even with the new element of Trump’s pledge to end former President Obama’s Deferred Action for Childhood Arrivals (DACA) program, any congressional attempt to resolve DACA recipients’ situation faces the same daunting legislative geometry that doomed the last two major attempts at comprehensive immigration reform in 2006 and 2013.

Those two congressional battles followed remarkably similar tracks, although the political alignment was very different: In 2006, Republicans controlled the White House and the Senate and in 2013, the Democrats controlled both. Critically, though, Republicans held the House both times.

In both 2006 and 2013, a bipartisan group of Senators crafted legislation whose central beam balanced tougher enforcement measures with a pathway to citizenship for 10-11 million undocumented immigrants, so long as they met certain conditions such as learning English. (Around that centerpiece, both bills also explicitly legalized those brought to the U.S. illegally as children, established a guest-worker program, and reformed legal immigration.) Every concerned interest group gnashed their teeth over some element of that composition, but business, organized labor, and immigrant advocacy groups locked arms behind the final product.

With that widespread institutional backing, and polls showing support from a clear majority of Americans, the Senate comfortably approved each bill. Each time Democrats provided most of the votes, but Republicans also contributed a sizable minority (23 votes in 2006 and 14 in 2013).

But each time the legislation hit the same wall in the House. Both times, vote counters agreed that something close to the Senate plan almost certainly had majority support in the full House. But because neither bill had support from most Republicans—the majority of the majority—House Speakers Denny Hastert in 2006 and John Boehner in 2013 refused to bring them to the floor.

Compared to the 2006 and 2013 experiences, it’s less certain that the Senate today can attract 60 votes for a bill protecting the Dreamers. The ferocity of Trump’s anti-immigration agenda has enormously widened the distance between the parties since then. Conservatives in Congress and the administration have already floated proposals to link any protection for Dreamers to some combination of cuts in legal immigration, funds for Trump’s border wall, tougher workplace enforcement, and harsher punishment for “sanctuary” cities that don’t fully cooperate with federal immigration enforcement demands.

Few Congressional Democrats would accept any of those ideas (especially since a bill covering DACA recipients would provide legal status to fewer than 10 percent as many undocumented immigrants as the earlier plans that traded legalization for more enforcement). Even the least objectionable way to marry a bill legalizing DACA recipients with enforcement—more dollars for immigration and border-patrol agents—would face more resistance on the left than in 2013 because the money would fund Trump’s enforcement agenda, not Obama’s.

“What’s different now is … we are experiencing the most terrorizing time and a time of persecution on immigrant communities and people of color,” said Cristina Jimenez, executive director of United We Dream, a advocacy group for DACA recipients, in a conference call Tuesday.

But the Senate may still find a way to thread the needle of blending legalization and enforcement. All public polls have found that about two-thirds or more of Americans—including just over half of Republicans—support legal status for DACA recipients. And the business community has condemned Trump’s action with striking unanimity; even the U.S. Chamber of Commerce, Trump’s most quiescent business ally, said rescinding protection for Dreamers “is contrary to fundamental American principles and … the president’s goal of growing the U.S. economy.” Facing such pressure, enough Senators could strike a deal that reaches 60 votes with support from almost all Democrats and a minority of Republicans.

But even if the Senate succeeds, House Speaker Paul Ryan will face the same choice as his predecessors. He could almost certainly pass legislation protecting DACA recipients if he relied mostly on Democratic votes. But to attract a majority of House Republicans he would likely need to attach much more biting enforcement provisions than a Senate bill would include. That process, though, could subtract more votes among Democrats than it adds among Republicans. Indeed, given how many House Republicans are unlikely to support legal status even if it’s coupled with more enforcement, history suggests there may not be any combination that could attract a majority in both the GOP caucus and the House overall.

The hard fact is that not enough House Republicans have ever felt a direct investment in the immigration debate to risk a backlash from the party’s nativist forces. (Over four-fifths of House Republicans represent districts where the immigrant population lags the national average.) Most have viewed inaction as safer than acting. Attorney General Jeff Sessions likely made them even more skittish with his vituperative statement Tuesday in which he argued (without evidence) that Obama’s DACA had encouraged more illegal immigration and stolen jobs from native-born young people.

Whether Congress protects the young people covered by DACA may turn on whether Ryan will do what Hastert and Boehner would not: pass a bill without support from a majority of House Republicans. (At his press briefing Wednesday, Ryan didn’t definitively commit on that pivotal question.) Ryan considers himself a disciple of the late Jack Kemp, committed to a racially inclusive GOP. But the speaker has been supine in resisting Trump’s increasingly overt appeals to white racial resentment. If Ryan lets the nativist right in his caucus veto a politically viable solution for DACA recipients, he will be digging the grave a little deeper for Kemp’s vision of a Republican Party open to all.